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Search for "kinetic isotope effect" in Full Text gives 26 result(s) in Beilstein Journal of Organic Chemistry.
Deuterated reagents in multicomponent reactions to afford deuterium-labeled products
- Kevin Schofield,
- Shayna Maddern,
- Yueteng Zhang,
- Grace E. Mastin,
- Rachel Knight,
- Wei Wang,
- James Galligan and
- Christopher Hulme
Beilstein J. Org. Chem. 2024, 20, 2270–2279, doi:10.3762/bjoc.20.195
- significantly enhanced metabolic stability, a key parameter for property-based design efforts. Keywords: deuterated aldehydes; deuterated formamides; deuterated isocyanides; DHPs; kinetic isotope effect; Leuckart–Wallach; microsomal stability; multicomponent reactions; Introduction Multicomponent reactions
- drug-like compounds with synthetic ease [5][6]. In recent years use of deuterium in drug discovery has expanded beyond mechanistic and tracer studies to deuterium incorporation in small molecules in attempts to hijack the deuterium kinetic isotope effect to induce longer drug t1/2 and greater systemic
- this position was thought a reasonable approach to extend drug t1/2 through exploitation of the kinetic isotope effect underpinned by the C–D bond being slightly shorter and stronger than a C–H bond. Such site-specific labeling was hypothesized to slow CYP3A4 metabolism. To evaluate the hypothesis
Graphical Abstract
Scheme 1: Competitive examples of D2-benzylamine formation via phenyl-nitriles.
Scheme 2: Proposed tentative mechanism of [D3]-formamide formation via modified Leuckart–Wallach reaction wit...
Scheme 3: Ugi-4CR products: no deuterium scrambling observed.
Scheme 4: Ugi-3CR products. No deuterium scrambling observed.
Scheme 5: Ugi-azide reaction products, no deuterium scrambling observed.
Scheme 6: Passerini products, no deuterium scrambling observed. aWater was used as solvent.
Scheme 7: Strecker reaction products (precursors to [D1]-α-amino acids), no deuterium scrambling was observed...
Scheme 8: Biginelli reaction products, no deuterium scrambling was observed. Six site-specific deuterated Big...
Scheme 9: GBB reaction products, no deuterium scrambling was observed. aA 70% [D2]-isocyanide was used in 7a ...
Scheme 10: Modified Hantzsch pyridine synthesis to afford 1,4-dihydropyridines. No deuterium scrambling was ob...
Scheme 11: CYP3A4 mediated dehydrogenation of dihydropyridines.
Ligand effects, solvent cooperation, and large kinetic solvent deuterium isotope effects in gold(I)-catalyzed intramolecular alkene hydroamination
- Ruichen Lan,
- Brock Yager,
- Yoonsun Jee,
- Cynthia S. Day and
- Amanda C. Jones
Beilstein J. Org. Chem. 2024, 20, 479–496, doi:10.3762/bjoc.20.43
- -order dependence on alkene, first-order dependence on catalyst, and second-order dependence on the imidazolidinone nucleophile [22]. They observed a primary kinetic isotope effect (k(H/D) = 3.14) when deuterated amine was used. The second order dependence is rationalized by a mechanism where a second
- . • At low incorporation of deuterium, there appears to be a balance between the influence on rate from N–H/N–D exchange and any release of H/DOR which also participates in the reaction. Partially deuterium-labeled urea 1a exhibits no primary kinetic isotope effect, however, trace amounts of protic water
Graphical Abstract
Scheme 1: Proposed mechanism and observation of alkylgold intermediates.
Figure 1: First order alkene decay for urea alkene 1a (0.05 M) hydroamination with [JPhosAu(NCCH3)]SbF6 (5, 2...
Figure 2: Cooperative effect of mixed CD2Cl2/MeOH on alkene 1a → 3a conversion with catalyst 5 (2.5 mol %). E...
Figure 3: Different additive impact on rate of 1a → 3a depending upon catalyst and co-solvent. The data for J...
Figure 4: (a) Schematic for synthesis of [L–Au–L]SbF6 where L = JPhos. (b) Perspective drawing of the cation ...
Figure 5: (a) kobs for reaction of urea 1a (0.05 M) in DCM with catalyst 5 and titrated CH3OH/CH3OD. Data for...
Figure 6: Rate of urea 1a (0.05 M) hydroamination with JPhosAu(NCCH3)SbF6 (2.5 mol %) in CH2Cl2 with 5, 25, a...
Figure 7: Observed rates for the reaction of carbamate 1b (0.03–0.24 M) with JackiephosAuNTf2 (0.0013 M, 6a) ...
Figure 8: Influence of catalyst 5 concentration on rate of 1a (0.05 M in CH2Cl2 with 0, 10 μL MeOH). Error ba...
Scheme 2: Proposed alternate mechanism.
Exploring the role of halogen bonding in iodonium ylides: insights into unexpected reactivity and reaction control
- Carlee A. Montgomery and
- Graham K. Murphy
Beilstein J. Org. Chem. 2023, 19, 1171–1190, doi:10.3762/bjoc.19.86
- formation of 33 and 35, implying that single electron-transfer processes were occurring. Also, a competition experiment between 32 and [D6]-32 gave a competitive intermolecular kinetic isotope effect of 9.5 that suggested an N-Me proton abstraction was the rate determining step. Given this, the authors
- ]. The authors discounted a free carbene-based C–H insertion because conducting the reaction in the presence of the radical trap phenyl N-tert-butyl nitrone (PBN) and the radical scavenger TEMPO resulted in decreased yields and isolation of their iodonium ylide adducts. Additional kinetic isotope effect
Graphical Abstract
Figure 1: Generic representation of halogen bonding.
Figure 2: Quantitative evaluation of σ-holes in monovalent iodine-containing compounds; and, qualitative mole...
Figure 3: Quantitative evaluation of σ-holes in hypervalent iodine-containing molecules; and, qualitative MEP...
Figure 4: Quantitative evaluation of σ-holes in iodonium ylides; and, qualitative MEP map of I-12 from −0.083...
Scheme 1: Outline of possible reaction pathways between iodonium ylides and Lewis basic nucleophiles (top); a...
Scheme 2: Metal-free cyclopropanations of iodonium ylides, either as intermolecular (a) or intramolecular pro...
Figure 5: Zwitterionic mechanism for intramolecular cyclopropanation of iodonium ylides (left); and, stepwise...
Scheme 3: Metal-free intramolecular cyclopropanation of iodonium ylides.
Figure 6: Concerted cycloaddition pathway for the metal-free, intramolecular cyclopropanation of iodonium yli...
Scheme 4: Reaction of ylide 6 with diphenylketene to form lactone 24 and 25.
Figure 7: Nucleophilic (top) and electrophilic (bottom) addition pathways proposed by Koser and Hadjiarapoglo...
Scheme 5: Indoline synthesis from acyclic iodonium ylide 31 and tertiary amines.
Scheme 6: N-Heterocycle synthesis from acyclic iodonium ylide 31 and secondary amines.
Figure 8: Proposed mechanism for the formation of 33a from iodonium ylides and amines, involving an initial h...
Scheme 7: Indoline synthesis from acyclic iodonium ylides 39 and tertiary amines under blue light photocataly...
Scheme 8: Metal-free cycloproponation of iodonium ylides under blue LED irradiation. aUsing trans-β-methylsty...
Figure 9: Proposed mechanism of the cyclopropanation between iodonium ylides and alkenes under blue LED irrad...
Scheme 9: Formal C–H alkylation of iodonium ylides by nucleophilic heterocycles under blue LED irradiation.
Figure 10: Proposed mechanism of the formal C–H insertion of pyrrole under blue LED irradiation.
Scheme 10: X–H insertions between iodonium ylides and carboxylic acids, phenols and thiophenols.
Figure 11: Mechanistic proposal for the X–H insertion reactions of iodonium ylides.
Scheme 11: Radiofluorination of biphenyl using iodonium ylides 54a–e derived from various β-dicarbonyl auxilia...
Scheme 12: Radiofluorination of arenes using spirocycle-derived iodonium ylides 56.
Scheme 13: Radiofluorination of arenes using SPIAd-derived iodonium ylides 58.
Figure 12: Calculated reaction coordinate for the radiofluorination of iodonium ylide 60.
Scheme 14: Radiofluorination of iodonium ylides possessing various ortho- and para-substituents on the iodoare...
Figure 13: Difference in Gibbs activation energy for ortho- or para-anisyl derived iodonium ylides 63a and 63b....
Figure 14: Proposed equilibration of intermediates to transit between 64a (the initial adduct formed between 6...
Scheme 15: Comparison of 31 and ortho-methoxy iodonium ylide 39 in rhodium-catalyzed cyclopropanation and cycl...
Figure 15: X-ray crystal structure of dimeric 39 [6], (CCDC# 893474) [143,144].
Scheme 16: Enaminone synthesis using diazonium and iodonium ylides.
Figure 16: Transition state calculations for enaminone synthesis from iodonium ylides and thioamides.
Scheme 17: The reaction between ylides 73a–f and N-methylpyrrole under 365 nm UV irradiation.
Figure 17: Crystal structures of 76c (top) and 76e (bottom) [101], (CCDC# 2104180 & 2104181) [143,144].
Photoredox catalysis harvesting multiple photon or electrochemical energies
- Mattia Lepori,
- Simon Schmid and
- Joshua P. Barham
Beilstein J. Org. Chem. 2023, 19, 1055–1145, doi:10.3762/bjoc.19.81
Graphical Abstract
Figure 1: Oxidative and reductive activations of organic compounds harvesting photoredox catalysis.
Figure 2: General catalytic cycles of radical ion conPET (left) and radical ion e-PRC (right).
Figure 3: “Beginner’s guide”: comparison between advantages, capacities, and prospectives of conPET and PEC.
Figure 4: A) conPET reductive dehalogenation of aryl halides with PDI. B) Reductive C–H arylation with pyrrol...
Figure 5: A) Chromoselective mono- and disubstitution or polybrominated pyrimidines with pyrroles. B) Sequent...
Figure 6: A) Synthesis of pyrrolo[1,2-a]quinolines. B) Synthesis of ullazines.
Figure 7: A) Reductive phosphorylation of aryl halides via conPET. B) Selected examples from the substrate sc...
Figure 8: A) Reductive dehalogenation of aryl halides via conPET and selected examples from the substrate sco...
Figure 9: A) Reductive C–H arylation of aryl halides via conPET (top) and selected examples from the substrat...
Figure 10: A) Reductive hydrodehalogenation of aryl halides with Mes-Acr-BF4. B) Selected examples from the su...
Figure 11: A) Reductive hydrodechlorination of aryl chlorides with 4-DPAIPN. B) Proposed formation of CO2•−. C...
Figure 12: A) Reductive conPET borylation with 3CzEPAIPN (top) and selected examples from the substrate scope ...
Figure 13: Scale-up of conPET phosphorylation with 3CzEPAIPN.
Figure 14: A) Borylation of 1d. B) Characteristics and structure of PC1 with green and red parts showing the l...
Figure 15: A) Reductive C–H arylation scope with polysulfide conPET (top) and selected examples from the subst...
Figure 16: Scale-up of A) C–H arylation and B) dehaloborylation with polysulfide photocatalysis in continuous-...
Figure 17: A) Formation of [Ir1]0 and [Ir2]0 upon PET between [Ir1]+ and Et3N. B) Mechanism of multi-photon ta...
Figure 18: A) Reductive hydrodehalogenation of aryl halides via multi-photon tandem photocatalysis. B) Selecte...
Figure 19: A) Carbonylative amidation of aryl halides in continuous flow. B) Selected examples from the substr...
Figure 20: A) General scheme for reductive (RQ) and oxidative quenching (OQ) protocols using [FeIII(btz)3](PF6)...
Figure 21: A) Carbonylative amidation of alkyl iodides with [IrIII(ppy)2(dtbbpy)]PF6. B) Selected examples fro...
Figure 22: A) Carboxylative C–N bond cleavage in cyclic amines. B) Selected examples from the substrate scope....
Figure 23: A) Formal reduction of alkenes to alkanes via transfer hydrogenation. B) Selected examples from the...
Figure 24: A) Birch-type reduction of benzenes with PMP-BPI. B) Selected examples from the substrate scope (sc...
Figure 25: Proposed mechanism of the OH− mediated conPET Birch-type reduction of benzene via generation of sol...
Figure 26: Reductive detosylation of N-tosylated amides with Mes-Acr-BF4. B) Selected examples from the substr...
Figure 27: A) Reductive detosylation of N-tosyl amides by dual PRC. B) Selected examples from the substrate sc...
Figure 28: A) Mechanism of the dual PRC based on PET between [Cu(dap)2]+ and DCA. B) Mechanism of the dual PRC...
Figure 29: A) N–O bond cleavage in Weinreb amides with anthracene. B) N–O bond cleavage in Weinreb amides rely...
Figure 30: A) Pentafluorosulfanylation and fluoride elimination. B) Mechanism of the pentafluorosulfanylation ...
Figure 31: A) α-Alkoxypentafluorosulfanylation (top) and selected examples from the substrate scope (bottom). ...
Figure 32: A) Oxidative amination of arenes with azoles catalyzed by N-Ph PTZ. B) Selected examples from the s...
Figure 33: A) C(sp3)–H bond activation by HAT via chloride oxidation by *N-Ph PTZ•+. B) Proposed mechanism for...
Figure 34: A) Recycling e-PRC C–H azolation of electron-rich arenes with pyrazoles using Mes-Acr+ as a photoca...
Figure 35: A) Radical ion e-PRC direct oxidation of unactivated arenes using TAC+ as an electro-activated phot...
Figure 36: A) Radical ion e-PRC direct oxidation of unactivated arenes using TPA as an electro-activated photo...
Figure 37: Proposed mechanism (top) and mode of preassembly (bottom).
Figure 38: A) Possible preassemblies of reactive (left) vs unreactive (right) arenes. B) Calculated spin densi...
Figure 39: A) Recycling e-PRC C(sp2 )–H acetoxylation of arenes using DDQ as a photocatalyst. B) Proposed cata...
Figure 40: Gram scale hydroxylation of benzene in a recirculated flow setup.
Figure 41: A) Radical ion e-PRC vicinal diamination of alkylarenes using TAC+ as an electro-activated photocat...
Figure 42: A) Sequential oxygenation of multiple adjacent C–H bonds under radical ion e-PRC using TAC+ as an e...
Figure 43: A) Enantioselective recycling e-PRC cyanation of benzylic C–H bonds using ADQS as photocatalyst. B)...
Figure 44: Proposed tandem mechanism by Xu and co-workers.
Figure 45: A) Enantioselective recycling e-PRC decarboxylative cyanation using Cu(acac)2, Ce(OTf)3 and a box l...
Figure 46: A) Enantioselective recycling e-PRC benzylic cyanation using Cu(MeCN)4BF4, box ligand and anthraqui...
Figure 47: A) Radical ion e-PRC acetoxyhydroxylation of aryl olefins using TAC+ as an electro-activated photoc...
Figure 48: Selected examples from the substrate scope.
Figure 49: Photoelectrochemical acetoxyhydroxylation in a recirculated flow setup.
Figure 50: A) Radical ion e-PRC aminooxygenation of aryl olefins using TAC+ as an electro-activated photocatal...
Figure 51: A) Recycling e-PRC C–H alkylation of heteroarenes with organic trifluoroborates using Mes-Acr+ as p...
Figure 52: A) Recycling e-PRC decarboxylative C–H alkylation of heteroarenes using CeCl3·7H2O as catalyst. B) ...
Figure 53: A) Recycling e-PRC decarboxylative C–H alkylation of heteroarenes using Fe(NH4)2(SO4)2·6H2O as cata...
Figure 54: A) Recycling e-PRC C–H alkylation of heteroarenes with alkyl oxalates and 4CzIPN as photocatalyst. ...
Figure 55: A) Recycling e-PRC decarboxylative C–H carbamoylation of heteroarenes using 4CzIPN as photocatalyst...
Figure 56: A) Photoelectrochemical HAT-mediated hydrocarbon activation via the chlorine radical. B) Proposed m...
Figure 57: A) Selected examples from the substrate scope. B) Gram and decagram scale semi-continuous flow PEC ...
Figure 58: A) Photoelectrochemical HAT-mediated dehydrogenative coupling of benzothiazoles with aliphatic C–H ...
Figure 59: A) Photoelectrochemical HAT activation of ethers using electro-activated TAC+ as photocatalyst. B) ...
Figure 60: Selected examples from the substrate scope.
Figure 61: A) Photoelectrochemical HAT-mediated synthesis of alkylated benzimidazo-fused isoquinolinones using...
Figure 62: A) Decoupled photoelectrochemical cerium-catalyzed oxydichlorination of alkynes using CeCl3 as cata...
Figure 63: Proposed decoupled photoelectrochemical mechanism.
Figure 64: A) Decoupled photoelectrochemical ring-opening bromination of tertiary cycloalkanols using MgBr2 as...
Figure 65: A) Recycling e-PRC ring-opening functionalization of cycloalkanols using CeCl3 as catalyst. B) Prop...
Figure 66: Selected examples from the substrate scope of the PEC ring-opening functionalization.
Figure 67: A) Radical ion e-PRC reduction of chloro- and bromoarenes using DCA as catalyst and various accepto...
Figure 68: A) Screening of different phthalimide derivatives as catalyst for the e-PRC reduction of aryl halid...
Figure 69: Screening of different organic catalysts for the e-PRC reduction of trialkylanilium salts.
Figure 70: A) e-PRC reduction of phosphonated phenols and anilinium salts. B) Selected examples from the subst...
Figure 71: A) ConPET and e-PRC reduction of 4-bromobenzonitrile using a naphthalene diimide (NDI) precatalyst ...
Figure 72: A) Radical ion e-PRC reduction of phosphinated aliphatic alcohols with n-BuO-NpMI as catalyst. B) C...
Figure 73: Selected examples from the substrate scope.
Figure 74: A) Recycling e-PRC reductive dimerization of benzylic chlorides using a [Cu2] catalyst. B) Proposed...
Figure 75: A) Decoupled photoelectrochemical C–H alkylation of heteroarenes through deamination of Katritzky s...
Figure 76: Proposed mechanism by Chen and co-workers.
Iron-catalyzed domino coupling reactions of π-systems
- Austin Pounder and
- William Tam
Beilstein J. Org. Chem. 2021, 17, 2848–2893, doi:10.3762/bjoc.17.196
- radical cyclization with the activated alkene 127. Ring closing with the ortho-carbon of the aryl ring generates aryl radical 128 which was confirmed not to be the rate-determining step by kinetic isotope effect studies. Subsequently, 128 is oxidized by S2O82− and deprotonated to form the desired product
Graphical Abstract
Figure 1: Price comparison among iron and other transition metals used in catalysis.
Scheme 1: Typical modes of C–C bond formation.
Scheme 2: The components of an iron-catalyzed domino reaction.
Scheme 3: Iron-catalyzed tandem cyclization and cross-coupling reactions of iodoalkanes 1 with aryl Grignard ...
Scheme 4: Three component iron-catalyzed dicarbofunctionalization of vinyl cyclopropanes 14.
Scheme 5: Three-component iron-catalyzed dicarbofunctionalization of alkenes 21.
Scheme 6: Double carbomagnesiation of internal alkynes 31 with alkyl Grignard reagents 32.
Scheme 7: Iron-catalyzed cycloisomerization/cross-coupling of enyne derivatives 35 with alkyl Grignard reagen...
Scheme 8: Iron-catalyzed spirocyclization/cross-coupling cascade.
Scheme 9: Iron-catalyzed alkenylboration of alkenes 50.
Scheme 10: N-Alkyl–N-aryl acrylamide 60 CDC cyclization with C(sp3)–H bonds adjacent to a heteroatom.
Scheme 11: 1,2-Carboacylation of activated alkenes 60 with aldehydes 65 and alcohols 67.
Scheme 12: Iron-catalyzed dicarbonylation of activated alkenes 68 with alcohols 67.
Scheme 13: Iron-catalyzed cyanoalkylation/radical dearomatization of acrylamides 75.
Scheme 14: Synergistic photoredox/iron-catalyzed 1,2-dialkylation of alkenes 82 with common alkanes 83 and 1,3...
Scheme 15: Iron-catalyzed oxidative coupling/cyclization of phenol derivatives 86 and alkenes 87.
Scheme 16: Iron-catalyzed carbosulfonylation of activated alkenes 60.
Scheme 17: Iron-catalyzed oxidative spirocyclization of N-arylpropiolamides 91 with silanes 92 and tert-butyl ...
Scheme 18: Iron-catalyzed free radical cascade difunctionalization of unsaturated benzamides 94 with silanes 92...
Scheme 19: Iron-catalyzed cyclization of olefinic dicarbonyl compounds 97 and 100 with C(sp3)–H bonds.
Scheme 20: Radical difunctionalization of o-vinylanilides 102 with ketones and esters 103.
Scheme 21: Dehydrogenative 1,2-carboamination of alkenes 82 with alkyl nitriles 76 and amines 105.
Scheme 22: Iron-catalyzed intermolecular 1,2-difunctionalization of conjugated alkenes 107 with silanes 92 and...
Scheme 23: Four-component radical difunctionalization of chemically distinct alkenes 114/115 with aldehydes 65...
Scheme 24: Iron-catalyzed carbocarbonylation of activated alkenes 60 with carbazates 117.
Scheme 25: Iron-catalyzed radical 6-endo cyclization of dienes 119 with carbazates 117.
Scheme 26: Iron-catalyzed decarboxylative synthesis of functionalized oxindoles 130 with tert-butyl peresters ...
Scheme 27: Iron‑catalyzed decarboxylative alkylation/cyclization of cinnamamides 131/134.
Scheme 28: Iron-catalyzed carbochloromethylation of activated alkenes 60.
Scheme 29: Iron-catalyzed trifluoromethylation of dienes 142.
Scheme 30: Iron-catalyzed, silver-mediated arylalkylation of conjugated alkenes 115.
Scheme 31: Iron-catalyzed three-component carboazidation of conjugated alkenes 115 with alkanes 101/139b and t...
Scheme 32: Iron-catalyzed carboazidation of alkenes 82 and alkynes 160 with iodoalkanes 20 and trimethylsilyl ...
Scheme 33: Iron-catalyzed asymmetric carboazidation of styrene derivatives 115.
Scheme 34: Iron-catalyzed carboamination of conjugated alkenes 115 with alkyl diacyl peroxides 163 and acetoni...
Scheme 35: Iron-catalyzed carboamination using oxime esters 165 and arenes 166.
Scheme 36: Iron-catalyzed iminyl radical-triggered [5 + 2] and [5 + 1] annulation reactions with oxime esters ...
Scheme 37: Iron-catalyzed decarboxylative alkyl etherification of alkenes 108 with alcohols 67 and aliphatic a...
Scheme 38: Iron-catalyzed inter-/intramolecular alkylative cyclization of carboxylic acid and alcohol-tethered...
Scheme 39: Iron-catalyzed intermolecular trifluoromethyl-acyloxylation of styrene derivatives 115.
Scheme 40: Iron-catalyzed carboiodination of terminal alkenes and alkynes 180.
Scheme 41: Copper/iron-cocatalyzed cascade perfluoroalkylation/cyclization of 1,6-enynes 183/185.
Scheme 42: Iron-catalyzed stereoselective carbosilylation of internal alkynes 187.
Scheme 43: Synergistic photoredox/iron catalyzed difluoroalkylation–thiolation of alkenes 82.
Scheme 44: Iron-catalyzed three-component aminoazidation of alkenes 82.
Scheme 45: Iron-catalyzed intra-/intermolecular aminoazidation of alkenes 194.
Scheme 46: Stereoselective iron-catalyzed oxyazidation of enamides 196 using hypervalent iodine reagents 197.
Scheme 47: Iron-catalyzed aminooxygenation for the synthesis of unprotected amino alcohols 200.
Scheme 48: Iron-catalyzed intramolecular aminofluorination of alkenes 209.
Scheme 49: Iron-catalyzed intramolecular aminochlorination and aminobromination of alkenes 209.
Scheme 50: Iron-catalyzed intermolecular aminofluorination of alkenes 82.
Scheme 51: Iron-catalyzed aminochlorination of alkenes 82.
Scheme 52: Iron-catalyzed phosphinoylazidation of alkenes 108.
Scheme 53: Synergistic photoredox/iron-catalyzed three-component aminoselenation of trisubstituted alkenes 82.
α-Ketol and α-iminol rearrangements in synthetic organic and biosynthetic reactions
- Scott Benz and
- Andrew S. Murkin
Beilstein J. Org. Chem. 2021, 17, 2570–2584, doi:10.3762/bjoc.17.172
- -xylulose-5-phosphate reductoisomerase (DXR), uses a different mechanism to accomplish the carbon-skeleton rearrangement of its substrate 63 [19]; kinetic isotope effect experiments have excluded an α-ketol rearrangement and instead support a stepwise retro-aldol/aldol sequence for formation of intermediate
Graphical Abstract
Figure 1: Generalized α-ketol or α-iminol rearrangement.
Figure 2: Nickel(II)-catalyzed enantioselective rearrangement of ketol 3 to form the ring-expanded and chiral...
Figure 3: Enantioselective ring expansion of β-hydroxy-α-dicarbonyl 6 catalyzed by a chiral copper-bisoxazoli...
Figure 4: Enantioselective rearrangement of ketols 9 and 12 and hydroxyaldimine 14 catalyzed by Al(III) or Sc...
Figure 5: Asymmetric rearrangement of α,α-dialkyl-α-siloxyaldehydes 16 to α-siloxyketones 17 catalyzed by chi...
Figure 6: BF3-promoted diastereospecific rearrangement of α-ketol 21 to difluoroalkoxyborane 22.
Figure 7: In the presence of a gold catalyst and water in 1,4-dioxane, 1-alkynylbutanol derivatives undergo t...
Figure 8: The diastereospecific α-ketol rearrangement of 32 to 33, part of the total synthesis of periconiano...
Figure 9: Two α-ketol rearrangements, one catalyzed by silica gel on 38 and the other by NaOMe on both 38 and ...
Figure 10: α-Ketol rearrangement of triumphalone (41) to isotriumphalone (42) via ring contraction.
Figure 11: Tandem reaction of strophasterol A synthetic intermediate 43 to 44 through a vinylogous α-ketol rea...
Figure 12: Tandem reaction consisting of a Diels–Alder cycloaddition followed by an α-ketol rearrangement, par...
Figure 13: Single-pot reaction consisting of Claisen and α-ketol rearrangements, part of the total synthesis o...
Figure 14: Enzyme-catalyzed α-ketol rearrangements. a) Ketol-acid reductoisomerase (KAR) catalyzes the rearran...
Figure 15: The conversion of asperfloroid (73) to asperflotone (72), featuring the ring-expanding α-ketol rear...
Figure 16: Hypothetical interconversion of natural products prekinamycin (76) and isoprekinamycin (77) and che...
Figure 17: Proposed biosynthetic pathway converting acylphloroglucinol (87) to isolated elodeoidins A–H 92–96....
Figure 18: α-Iminol rearrangements catalyzed by VANOL Zr (99). The rearrangement can be conducted with preform...
Figure 19: α-Iminol rearrangements catalyzed by silica gel and montmorillonite K 10. a) For 102a (102 with R =...
Figure 20: Synthesis of tryptamines 110 via a ring-contracting α‑iminol rearrangement. A mechanism for the fin...
Figure 21: Tandem synthesis of functionalized α-amino cyclopentanones 119 from heteroarenes 115 and cyclobutan...
Figure 22: Four eburnane-type alkaloid natural products 122–125 were synthesized from common intermediate 127,...
Copper-catalyzed monoselective C–H amination of ferrocenes with alkylamines
- Zhen-Sheng Jia,
- Qiang Yue,
- Ya Li,
- Xue-Tao Xu,
- Kun Zhang and
- Bing-Feng Shi
Beilstein J. Org. Chem. 2021, 17, 2488–2495, doi:10.3762/bjoc.17.165
- exchange was observed at the ortho-position of 1a with 3.0 equivalents of CD3CO2D under standard conditions (Scheme 5a). Furthermore, a larger value of kinetic isotope effect (KIE = 2.4) was detected (Scheme 5b). These results indicated that the cleavage of C–H bond was most likely involved in the rate
Graphical Abstract
Scheme 1: 3d-Transition-metal-catalyzed C–H functionalization to access functionalized ferrocenes.
Scheme 2: Scope of ferrocenes with morpholine.
Scheme 3: Scope of various amines with 1a.
Scheme 4: Synthetic applications.
Scheme 5: Mechanistic experiments.
Copper-mediated oxidative C−H/N−H activations with alkynes by removable hydrazides
- Feng Xiong,
- Bo Li,
- Chenrui Yang,
- Liang Zou,
- Wenbo Ma,
- Linghui Gu,
- Ruhuai Mei and
- Lutz Ackermann
Beilstein J. Org. Chem. 2021, 17, 1591–1599, doi:10.3762/bjoc.17.113
- -position of the reisolated benzhydrazide 1c and product 3ca when the reaction was conducted with the isotopically labeled D2O as cosolvent (Scheme 4c). This observation indicated that the C−H cleavage is irreversible. In accordance with this finding, a kinetic isotope effect (KIE) of kH/kD ≈ 6.1 was
Graphical Abstract
Figure 1: Assembly of 3-methyleneisoindolin-1-one via 3d transition metal-mediated/catalyzed oxidative C−H/N−...
Scheme 1: Copper-mediated oxidative C−H/N−H functionalization of hydrazides 1 with ethynylbenzene (2a).
Scheme 2: Copper-mediated oxidative C−H/N−H functionalization of 1 with alkynes 2.
Scheme 3: Decaboxylative C−H/N−H activation and cleavage of the directing group.
Scheme 4: Summary of key mechanistic findings.
Scheme 5: Proposed reaction pathway.
Methodologies for the synthesis of quaternary carbon centers via hydroalkylation of unactivated olefins: twenty years of advances
- Thiago S. Silva and
- Fernando Coelho
Beilstein J. Org. Chem. 2021, 17, 1565–1590, doi:10.3762/bjoc.17.112
- methylcycloalkanes (94a and 94b) and the terminal olefin 93 (Scheme 37A). Both examples showed perfect regioselectivity for the functionalization of the tertiary C(sp3)–H bond. Mechanistic studies carried out by the authors revealed a strong kinetic isotope effect (KIE = 11.5:1) when a competitive reaction was
Graphical Abstract
Figure 1: Some examples of natural products and drugs containing quaternary carbon centers.
Scheme 1: Simplified mechanism for olefin hydrofunctionalization using an electrophilic transition metal as a...
Scheme 2: Selected examples of quaternary carbon centers formed by the intramolecular hydroalkylation of β-di...
Scheme 3: Control experiments and the proposed mechanism for the Pd(II)-catalyzed intermolecular hydroalkylat...
Scheme 4: Intermolecular olefin hydroalkylation of less reactive ketones under Pd(II) catalysis using HCl as ...
Scheme 5: A) Selected examples of Pd(II)-mediated quaternary carbon center synthesis by intermolecular hydroa...
Scheme 6: Selected examples of quaternary carbon center synthesis by gold(III) catalysis. This is the first r...
Scheme 7: Selected examples of inter- (A) and intramolecular (B) olefin hydroalkylations promoted by a silver...
Scheme 8: A) Intermolecular hydroalkylation of N-alkenyl β-ketoamides under Au(I) catalysis in the synthesis ...
Scheme 9: Asymmetric pyrrolidine synthesis through intramolecular hydroalkylation of α-substituted N-alkenyl ...
Scheme 10: Proposed mechanism for the chiral gold(I) complex promotion of the intermolecular olefin hydroalkyl...
Scheme 11: Selected examples of carbon quaternary center synthesis by gold and evidence of catalytic system pa...
Scheme 12: Synthesis of a spiro compound via an aza-Michael addition/olefin hydroalkylation cascade promoted b...
Scheme 13: A selected example of quaternary carbon center synthesis using an Fe(III) salt as a catalyst for th...
Scheme 14: Intermolecular hydroalkylation catalyzed by a cationic iridium complex (Fuji (2019) [47]).
Scheme 15: Generic example of an olefin hydrofunctionalization via MHAT (Shenvi (2016) [51]).
Scheme 16: The first examples of olefin hydrofunctionalization run under neutral conditions (Mukaiyama (1989) [56]...
Scheme 17: A) Aryl olefin dimerization catalyzed by vitamin B12 and triggered by HAT. B) Control experiment to...
Scheme 18: Generic example of MHAT diolefin cycloisomerization and possible competitive pathways. Shenvi (2014...
Scheme 19: Selected examples of the MHAT-promoted cycloisomerization reaction of unactivated olefins leading t...
Scheme 20: Regioselective carbocyclizations promoted by an MHAT process (Norton (2008) [76]).
Scheme 21: Selected examples of quaternary carbon centers synthetized via intra- (A) and intermolecular (B) MH...
Scheme 22: A) Proposed mechanism for the Fe(III)/PhSiH3-promoted radical conjugate addition between olefins an...
Scheme 23: Examples of cascade reactions triggered by HAT for the construction of trans-decalin backbone uniti...
Scheme 24: A) Selected examples of the MHAT-promoted radical conjugate addition between olefins and p-quinone ...
Scheme 25: A) MHAT triggered radical conjugate addition/E1cB/lactonization (in some cases) cascade between ole...
Scheme 26: A) Spirocyclization promoted by Fe(III) hydroalkylation of unactivated olefins. B) Simplified mecha...
Scheme 27: A) Selected examples of the construction of a carbon quaternary center by the MHAT-triggered radica...
Scheme 28: Hydromethylation of unactivated olefins under iron-mediated MHAT (Baran (2015) [95]).
Scheme 29: The hydroalkylation of unactivated olefins via iron-mediated reductive coupling with hydrazones (Br...
Scheme 30: Selected examples of the Co(II)-catalyzed bicyclization of dialkenylarenes through the olefin hydro...
Scheme 31: Proposed mechanism for the bicyclization of dialkenylarenes triggered by a MHAT process (Vanderwal ...
Scheme 32: Enantioconvergent cross-coupling between olefins and tertiary halides (Fu (2018) [108]).
Scheme 33: Proposed mechanism for the Ni-catalyzed cross-coupling reaction between olefins and tertiary halide...
Scheme 34: Proposed catalytic cycles for a MHAT/Ni cross-coupling reaction between olefins and halides (Shenvi...
Scheme 35: Selected examples of the hydroalkylation of olefins by a dual catalytic Mn/Ni system (Shenvi (2019) ...
Scheme 36: A) Selected examples of quaternary carbon center synthesis by reductive atom transfer; TBC: 4-tert-...
Scheme 37: A) Selected examples of quaternary carbon centers synthetized by radical addition to unactivated ol...
Scheme 38: A) Selected examples of organophotocatalysis-mediated radical polyene cyclization via a PET process...
Scheme 39: A) Sc(OTf)3-mediated carbocyclization approach for the synthesis of vicinal quaternary carbon cente...
Scheme 40: Scope of the Lewis acid-catalyzed methallylation of electron-rich styrenes. Method A: B(C6F5)3 (5.0...
Scheme 41: The proposed mechanism for styrene methallylation (Oestreich (2019) [123]).
CF3-substituted carbocations: underexploited intermediates with great potential in modern synthetic chemistry
- Anthony J. Fernandes,
- Armen Panossian,
- Bastien Michelet,
- Agnès Martin-Mingot,
- Frédéric R. Leroux and
- Sébastien Thibaudeau
Beilstein J. Org. Chem. 2021, 17, 343–378, doi:10.3762/bjoc.17.32
- )carbenium ion. Further studies were conducted by Lenoir and Dahn to shed light on the mechanism of the solvolysis of CF3-substituted diazoalkane derivatives (Figure 10a) [144]. They measured an inverse kinetic isotope effect of kH/kD = 0.25 for the solvolysis of 217a in dioxane/H2O 60:40 in the presence of
Graphical Abstract
Figure 1: Stabilizing interaction in the CF3CH2+ carbenium ion (top) and structure of the first observable fl...
Scheme 1: Isodesmic equations accounting for the destabilizing effect of the CF3 group. ΔE in kcal⋅mol−1, cal...
Scheme 2: Stabilizing effect of fluorine atoms by resonance electron donation in carbenium ions (δ in ppm).
Scheme 3: Direct in situ NMR observation of α-(trifluoromethyl)carbenium ion or protonated alcohols. Δδ = δ19...
Scheme 4: Reported 13C NMR chemical shifts for the α-(trifluoromethyl)carbenium ion 10c (δ in ppm).
Scheme 5: Direct NMR observation of α-(trifluoromethyl)carbenium ions in situ (δ in ppm).
Scheme 6: Illustration of the ion pair solvolysis mechanism for sulfonate 13f. YOH = solvent.
Figure 2: Solvolysis rate for 13a–i and 17.
Figure 3: Structures of allyl triflates 18 and 19 and allyl brosylate 20. Bs = p-BrC6H4SO2.
Figure 4: Structure of tosylate derivatives 21.
Figure 5: a) Structure of triflate derivatives 22. b) Stereochemistry outcomes of the reaction starting from (...
Scheme 7: Solvolysis reaction of naphthalene and anthracenyl derivatives 26 and 29.
Figure 6: Structure of bisarylated derivatives 34.
Figure 7: Structure of bisarylated derivatives 36.
Scheme 8: Reactivity of 9c in the presence of a Brønsted acid.
Scheme 9: Cationic electrocyclization of 38a–c under strongly acidic conditions.
Scheme 10: Brønsted acid-catalyzed synthesis of indenes 42 and indanes 43.
Scheme 11: Reactivity of sulfurane 44 in triflic acid.
Scheme 12: Solvolysis of triflate 45f in alcoholic solvents.
Scheme 13: Synthesis of labeled 18O-52.
Scheme 14: Reactivity of sulfurane 53 in triflic acid.
Figure 8: Structure of tosylates 56 and 21f.
Scheme 15: Resonance forms in benzylic carbenium ions.
Figure 9: Structure of pyrrole derivatives 58 and 59.
Scheme 16: Resonance structure 60↔60’.
Scheme 17: Ga(OTf)3-catalyzed synthesis of 3,3’- and 3,6’-bis(indolyl)methane from trifluoromethylated 3-indol...
Scheme 18: Proposed reaction mechanism.
Scheme 19: Metal-free 1,2-phosphorylation of 3-indolylmethanols.
Scheme 20: Superacid-mediated arylation of thiophene derivatives.
Scheme 21: In situ mechanistic NMR investigations.
Scheme 22: Proposed mechanisms for the prenyltransferase-catalyzed condensation.
Scheme 23: Influence of a CF3 group on the allylic SN1- and SN2-mechanism-based reactions.
Scheme 24: Influence of the CF3 group on the condensation reaction.
Scheme 25: Solvolysis of 90 in TFE.
Scheme 26: Solvolysis of allyl triflates 94 and 97 and isomerization attempt of 96.
Scheme 27: Proposed mechanism for the formation of 95.
Scheme 28: Formation of α-(trifluoromethyl)allylcarbenium ion 100 in a superacid.
Scheme 29: Lewis acid activation of CF3-substituted allylic alcohols.
Scheme 30: Bimetallic-cluster-stabilized α-(trifluoromethyl)carbenium ions.
Scheme 31: Reactivity of cluster-stabilized α-(trifluoromethyl)carbenium ions.
Scheme 32: α-(Trifluoromethyl)propargylium ion 122↔122’ generated from silyl ether 120 in a superacid.
Scheme 33: Formation of α-(trifluoromethyl)propargylium ions from CF3-substituted propargyl alcohols.
Scheme 34: Direct NMR observation of the protonation of some trifluoromethyl ketones in situ and the correspon...
Scheme 35: Selected resonance forms in protonated fluoroketone derivatives.
Scheme 36: Acid-catalyzed Friedel–Crafts reactions of trifluoromethyl ketones 143a,b and 147a–c.
Scheme 37: Enantioselective hydroarylation of CF3-substituted ketones.
Scheme 38: Acid-catalyzed arylation of ketones 152a–c.
Scheme 39: Reactivity of 156 in a superacid.
Scheme 40: Reactivity of α-CF3-substituted heteroaromatic ketones and alcohols as well as 1,3-diketones.
Scheme 41: Reactivity of 168 with benzene in the presence of a Lewis or Brønsted acid.
Scheme 42: Acid-catalyzed three-component asymmetric reaction.
Scheme 43: Anodic oxidation of amines 178a–c and proposed mechanism.
Scheme 44: Reactivity of 179b in the presence of a strong Lewis acid.
Scheme 45: Trifluoromethylated derivatives as precursors of trifluoromethylated iminium ions.
Scheme 46: Mannich reaction with trifluoromethylated hemiaminal 189.
Scheme 47: Suitable nucleophiles reacting with 192 after Lewis acid activation.
Scheme 48: Strecker reaction involving the trifluoromethylated iminium ion 187.
Scheme 49: Reactivity of 199 toward nucleophiles.
Scheme 50: Reactivity of 204a with benzene in the presence of a Lewis acid.
Scheme 51: Reactivity of α-(trifluoromethyl)-α-chloro sulfides in the presence of strong Lewis acids.
Scheme 52: Anodic oxidation of sulfides 213a–h and Pummerer rearrangement.
Scheme 53: Mechanism for the electrochemical oxidation of the sulfide 213a.
Scheme 54: Reactivity of (trifluoromethyl)diazomethane (217a) in HSO3F.
Figure 10: a) Structure of diazoalkanes 217a–c and b) rate-limiting steps of their decomposition.
Scheme 55: Deamination reaction of racemic 221 and enantioenriched (S)-221.
Scheme 56: Deamination reaction of labeled 221-d2. Elimination products were formed in this reaction, the yiel...
Scheme 57: Deamination reaction of 225-d2. Elimination products were also formed in this reaction in undetermi...
Scheme 58: Formation of 229 from 228 via 1,2-H-shift.
Scheme 59: Deamination reaction of 230. Elimination products were formed in this reaction, the yield of which ...
Scheme 60: Deamination of several diazonium ions. Elimination products were formed in these reactions, the yie...
Scheme 61: Solvolysis reaction mechanism of alkyl tosylates.
Scheme 62: Solvolysis outcome for the tosylates 248 and 249 in HSO3FSbF5.
Figure 11: Solvolysis rate of 248, 249, 252, and 253 in 91% H2SO4.
Scheme 63: Illustration of the reaction pathways. TsCl, pyridine, −5 °C (A); 98% H2SO4, 30 °C (B); 98% H2SO4, ...
Scheme 64: Proposed solvolysis mechanism for the aliphatic tosylate 248.
Scheme 65: Solvolysis of the derivatives 259 and 260.
Scheme 66: Solvolysis of triflate 261. SOH = solvent.
Scheme 67: Intramolecular Friedel–Crafts alkylations upon the solvolysis of triflates 264 and 267.
Scheme 68: α-CF3-enhanced γ-silyl elimination of cyclobutyltosylates 270a,b.
Scheme 69: γ-Silyl elimination in the synthesis of a large variety of CF3-substituted cyclopropanes. Pf = pent...
Scheme 70: Synthetic pathways to 281. aNMR yields.
Scheme 71: The cyclopropyl-substituted homoallylcyclobutylcarbenium ion manifold.
Scheme 72: Reactivity of CF3-substituted cyclopropylcarbinyl derivatives 287a–c. LG = leaving group.
Scheme 73: Reactivity of CF3-substituted cyclopropylcarbinyl derivatives 291a–c.
Scheme 74: Superacid-promoted dimerization or TFP.
Scheme 75: Reactivity of TFP in a superacid.
Scheme 76: gem-Difluorination of α-fluoroalkyl styrenes via the formation of a “hidden” α-RF-substituted carbe...
Scheme 77: Solvolysis of CF3-substituted pentyne 307.
Scheme 78: Photochemical rearrangement of 313.
Figure 12: Structure of 2-norbornylcarbenium ion 318 and argued model for the stabilization of this cation.
Figure 13: Structures and solvolysis rate (TFE, 25 °C) of the sulfonates 319–321. Mos = p-MeOC6H4SO2.
Scheme 79: Mechanism for the solvolysis of 323. SOH = solvent.
Scheme 80: Products formed by the hydrolysis of 328.
Scheme 81: Proposed carbenium ion intermediates in an equilibrium during the solvolysis of tosylates 328, 333,...
A dynamic combinatorial library for biomimetic recognition of dipeptides in water
- Florian Klepel and
- Bart Jan Ravoo
Beilstein J. Org. Chem. 2020, 16, 1588–1595, doi:10.3762/bjoc.16.131
- (Figure S10, Supporting Information File 1). This behavior does not contradict the ITC measurements and can be attributed to the kinetic isotope effect. Although, D-bonding is generally stronger than H-bonding, its contribution to the peptide–peptide binding can be weakened by even stronger competitive
Graphical Abstract
Scheme 1: a) Building blocks included in this study. b) Antiparallel and parallel constitutional isomers of t...
Figure 1: HPLC–MS chromatograms of a reference library for all possible tripeptide dimers ([M + H]+ ions).
Figure 2: a) HPLC–MS chromatograms of the dimers (CFC)2 and templates YY and FF. b) Amplification of the peak...
Scheme 2: a) Synthesis of the parallel and antiparallel isomers p(CFC)2 and a(CFC)2. b) Templates FF. YY and ...
Figure 3: ITC of YY (30 mM) to a(CFC)2 (1.5 mM) in phosphate buffer (pH 7.4, 100 mM).
Figure 4: Continuously varied NMR measurements of a) p(CFC)2 to YY b) p(CFC)2 to FF c) a(CFC)2 to YY d) a(CFC)...
Figure 5: Job plots derived from the continuously varied NMR measurements of a) p(CFC)2 to YY b) p(CFC)2 to FF...
Recent developments in photoredox-catalyzed remote ortho and para C–H bond functionalizations
- Rafia Siddiqui and
- Rashid Ali
Beilstein J. Org. Chem. 2020, 16, 248–280, doi:10.3762/bjoc.16.26
- substituents (Scheme 5), and (v) the rate-determining step (i.e., breaking of the C–H bond) was suggested to follow a first-order kinetic isotope effect (KH/KD = 5). As such, a library of benzothiazole derivatives was reported using this methodology, and a plausible mechanism is shown in Figure 9. Synthesis of
Graphical Abstract
Figure 1: List of photoredox catalysts used for C–H bond functionalizations.
Figure 2: List of metal-based photoredox catalysts used in this review article.
Figure 3: Jablonski diagram.
Figure 4: Photoredox catalysis via reductive or oxidative pathways. D = donor, A = acceptor, S = substrate, P...
Figure 5: Schematic representation of the combination of photoredox catalysis and transition metal catalysis.
Scheme 1: Weinreb amide C–H olefination.
Figure 6: Mechanism for the formation of 21 from 19 using photoredox catalyst 11.
Scheme 2: C–H olefination of phenolic ethers.
Scheme 3: Decarboxylative acylation of acetanilides.
Figure 7: Mechanism for the formation of 30 from acetanilide derivatives.
Scheme 4: Synthesis of fluorenone derivatives by intramolecular deoxygenative acylation of biaryl carboxylic ...
Figure 8: Mechanism for the photoredox-catalyzed synthesis of fluorenone derivatives.
Scheme 5: Synthesis of benzothiazoles via aerobic C–H thiolation.
Figure 9: Plausible mechanism for the construction of benzothiazoles from benzothioamides.
Scheme 6: Synthesis of benzothiazoles via oxidant-free C–H thiolation.
Figure 10: Mechanism involved in the synthesis of benzothiazoles via oxidant-free C–H thiolation.
Scheme 7: Synthesis of indoles via C–H cyclization of anilides with alkynes.
Scheme 8: Preparation of 3-trifluoromethylcoumarins via C–H cyclization of arylpropiolate esters.
Figure 11: Mechanistic pathway for the synthesis of coumarin derivatives via C–H cyclization.
Scheme 9: Monobenzoyloxylation without chelation assistance.
Figure 12: Plausible mechanism for the formation of 71 from 70.
Scheme 10: Aryl-substituted arenes prepared by inorganic photoredox catalysis using 12a.
Figure 13: Proposed mechanism for C–H arylations in the presence of 12a and a Pd catalyst.
Scheme 11: Arylation of purines via dual photoredox catalysis.
Scheme 12: Arylation of substituted arenes with an organic photoredox catalyst.
Scheme 13: C–H trifluoromethylation.
Figure 14: Proposed mechanism for the trifluoromethylation of 88.
Scheme 14: Synthesis of benzo-3,4-coumarin derivatives.
Figure 15: Plausible mechanism for the synthesis of substituted coumarins.
Scheme 15: Oxidant-free oxidative phosphonylation.
Figure 16: Mechanism proposed for the phosphonylation reaction of 100.
Scheme 16: Nitration of anilines.
Figure 17: Plausible mechanism for the nitration of aniline derivatives via photoredox catalysis.
Scheme 17: Synthesis of carbazoles via intramolecular amination.
Figure 18: Proposed mechanism for the formation of carbazoles from biaryl derivatives.
Scheme 18: Synthesis of substituted phenols using QuCN.
Figure 19: Mechanism for the synthesis of phenol derivatives with photoredox catalyst 8.
Scheme 19: Synthesis of substituted phenols with DDQ (5).
Figure 20: Possible mechanism for the generation of phenols with the aid of photoredox catalyst 5.
Scheme 20: Aerobic bromination of arenes using an acridinium-based photocatalyst.
Scheme 21: Aerobic bromination of arenes with anthraquinone.
Figure 21: Proposed mechanism for the synthesis of monobrominated compounds.
Scheme 22: Chlorination of benzene derivatives with Mes-Acr-MeClO4 (2).
Figure 22: Mechanism for the synthesis of 131 from 132.
Scheme 23: Chlorination of arenes with 4CzIPN (5a).
Figure 23: Plausible mechanism for the oxidative photocatalytic monochlorination using 5a.
Scheme 24: Monofluorination using QuCN-ClO4 (8).
Scheme 25: Fluorination with fluorine-18.
Scheme 26: Aerobic amination with acridinium catalyst 3a.
Figure 24: Plausible mechanism for the aerobic amination using acridinium catalyst 3a.
Scheme 27: Aerobic aminations with semiconductor photoredox catalyst 18.
Scheme 28: Perfluoroalkylation of arenes.
Scheme 29: Synthesis of benzonitriles in the presence of 3a.
Figure 25: Plausible mechanism for the synthesis of substituted benzonitrile derivatives in the presence of 3a....
Selective benzylic C–H monooxygenation mediated by iodine oxides
- Kelsey B. LaMartina,
- Haley K. Kuck,
- Linda S. Oglesbee,
- Asma Al-Odaini and
- Nicholas C. Boaz
Beilstein J. Org. Chem. 2019, 15, 602–609, doi:10.3762/bjoc.15.55
- via a similar mechanism we examined several aspects of the NHPI-iodate system. A substrate deuterium kinetic isotope effect (KIE) study indicated that the benzylic C–H bond is broken more rapidly than the C–D bond of the deuterated substrate. Catalytic oxidation of a stoichiometric mixture of proteo
Graphical Abstract
Figure 1: Catalyst optimization for the monooxidation of n-butylbenzene mediated by the iodate anion.
Figure 2: NHPI-catalyzed oxidation of secondary benzylic C–H bonds mediated by iodine(V). a100 °C for 18 h; b...
Figure 3: NHPI-catalyzed oxidation of di-benzylic C–H bonds mediated by iodate.
Figure 4: NHPI-catalyzed oxidation of substrates containing primary and tertiary benzylic C–H bonds. aReactio...
Figure 5: Competitive deuterium KIE for the oxidation of ethyl benzene by the NHPI-iodate system.
Figure 6: Pyrolysis of an acyl perester in the presence of molecular iodine.
Figure 7: Proposed mechanism for the selective monooxygenation of benzylic C–H bonds.
A challenging redox neutral Cp*Co(III)-catalysed alkylation of acetanilides with 3-buten-2-one: synthesis and key insights into the mechanism through DFT calculations
- Andrew Kenny,
- Alba Pisarello,
- Arron Bird,
- Paula G. Chirila,
- Alex Hamilton and
- Christopher J. Whiteoak
Beilstein J. Org. Chem. 2018, 14, 2366–2374, doi:10.3762/bjoc.14.212
- energy difference between the C–H activation and C–C bond formation steps makes identification of the rate limiting step difficult by DFT calculations alone, however, parallel kinetic isotope effect (KIE) experiments do suggest that the C–H activation step is not rate limiting (KIE = 1.3), which is not
Graphical Abstract
Scheme 1: (a) Our previously reported Cp*Co(III) redox-neutral coupling of 3-buten-2-one to benzamides, (b) p...
Scheme 2: Summary of reaction conditions optimisation.
Scheme 3: Substrate scope of Cp*Co(III)-catalysed coupling of 3-buten-2-one with functionalised acetanilides....
Figure 1: Mechanistic pathway for Cp*Co(III)-catalysed alkylation of acetanilide with 3-buten-2-one obtained ...
Figure 2: Comparison between energies during the Cp*Co(III)-catalysed coupling of 3-buten-2-one with acetanil...
Figure 3: Comparative visualisation of bcp for Int 2ketone with the acetanilide (left) and benzamide substrat...
Scheme 4: Competitive experiment between coupling to acetanilide (ring A) or benzamide (ring B). aMajor produ...
Hydroarylations by cobalt-catalyzed C–H activation
- Rajagopal Santhoshkumar and
- Chien-Hong Cheng
Beilstein J. Org. Chem. 2018, 14, 2266–2288, doi:10.3762/bjoc.14.202
- found intermolecular kinetic isotope effect (KIE) of kH/kD = 2.1 and H/D crossover studies strongly suggest that the reaction proceeds through an oxidative addition of a C–H bond to low-valent cobalt followed by alkyne insertion and reductive elimination. Furthermore, the new C–C bond formation occurred
Graphical Abstract
Scheme 1: Cobalt-catalyzed C–H carbonylation.
Scheme 2: Hydroarylation by C–H activation.
Scheme 3: Pathways for cobalt-catalyzed hydroarylations.
Scheme 4: Co-catalyzed hydroarylation of alkynes with azobenzenes.
Scheme 5: Co-catalyzed hydroarylation of alkynes with 2-arylpyridines.
Scheme 6: Co-catalyzed addition of azoles to alkynes.
Scheme 7: Co-catalyzed addition of indoles to alkynes.
Scheme 8: Co-catalyzed hydroarylation of alkynes with imines.
Scheme 9: A plausible pathway for Co-catalyzed hydroarylation of alkynes.
Scheme 10: Co-catalyzed anti-selective C–H addition to alkynes.
Scheme 11: Co(III)-catalyzed hydroarylation of alkynes with indoles.
Scheme 12: Co(III)-catalyzed branch-selective hydroarylation of alkynes.
Scheme 13: Co(III)-catalyzed hydroarylation of terminal alkynes with arenes.
Scheme 14: Co(III)-catalyzed hydroarylation of alkynes with amides.
Scheme 15: Co(III)-catalyzed C–H alkenylation of arenes.
Scheme 16: Co-catalyzed alkylation of substituted benzamides with alkenes.
Scheme 17: Co-catalyzed switchable hydroarylation of styrenes with 2-aryl pyridines.
Scheme 18: Co-catalyzed linear-selective hydroarylation of alkenes with imines.
Scheme 19: Co-catalyzed linearly-selective hydroarylation of alkenes with N–H imines.
Scheme 20: Co-catalyzed branched-selective hydroarylation of alkenes with imines.
Scheme 21: Mechanism of Co-catalyzed hydroarylation of alkenes.
Scheme 22: Co-catalyzed intramolecular hydroarylation of indoles.
Scheme 23: Co-catalyzed asymmetric hydroarylation of alkenes with indoles.
Scheme 24: Co-catalyzed hydroarylation of alkenes with heteroarenes.
Scheme 25: Co(III)-catalyzed hydroarylation of activated alkenes with 2-phenyl pyridines.
Scheme 26: Co(III)-catalyzed C–H alkylation of arenes.
Scheme 27: Co(III)-catalyzed C2-alkylation of indoles.
Scheme 28: Co(III)-catalyzed switchable hydroarylation of alkyl alkenes with indoles.
Scheme 29: Co(III)-catalyzed C2-allylation of indoles.
Scheme 30: Co(III)-catalyzed ortho C–H alkylation of arenes with maleimides.
Scheme 31: Co(III)-catalyzed hydroarylation of maleimides with arenes.
Scheme 32: Co(III)-catalyzed hydroarylation of allenes with arenes.
Scheme 33: Co-catalyzed hydroarylative cyclization of enynes with carbonyl compounds.
Scheme 34: Mechanism for the Co-catalyzed hydroarylative cyclization of enynes with carbonyl compounds.
Scheme 35: Co-catalyzed addition of 2-arylpyridines to aromatic aldimines.
Scheme 36: Co-catalyzed addition of 2-arylpyridines to aziridines.
Scheme 37: Co(III)-catalyzed hydroarylation of imines with arenes.
Scheme 38: Co(III)-catalyzed addition of arenes to ketenimines.
Scheme 39: Co(III)-catalyzed three-component coupling.
Scheme 40: Co(III)-catalyzed hydroarylation of aldehydes.
Scheme 41: Co(III)-catalyzed addition of arenes to isocyanates.
Phosphodiester models for cleavage of nucleic acids
- Satu Mikkola,
- Tuomas Lönnberg and
- Harri Lönnberg
Beilstein J. Org. Chem. 2018, 14, 803–837, doi:10.3762/bjoc.14.68
- enzyme–substrate interaction is not distorted, which is the case with other structural modifications. Kinetic isotope effect is defined as the ratio of the rate constants obtained with the light and heavy isotope containing compound, KIE = lightk/heavyk. When this ratio is greater than unity, the isotope
Graphical Abstract
Figure 1: Enzymatic cleavage of phosphodiester linkages of DNA and RNA.
Figure 2: Energy profiles for a concerted ANDN (A) and stepwise mechanisms (AN + DN) with rate-limiting break...
Figure 3: Pseudorotation of a trigonal bipyramidal phosphorane intermediate by Berry pseudorotation [20].
Figure 4: Protolytic equilibria of phosphorane intermediate of RNA transesterification.
Figure 5: Structures of acyclic analogs of ribonucleosides.
Figure 6: First-order rate constants for buffer-independent partial reactions of uridyl-3´,5´-uridine at pH 5...
Scheme 1: pH- and buffer-independent cleavage and isomerization of RNA phosphodiester linkages. Observed firs...
Scheme 2: Mechanism for the pH- and buffer-independent cleavage of RNA phosphodiester linkages.
Scheme 3: Hydroxide-ion-catalyzed cleavage of RNA phosphodiester linkages.
Scheme 4: Anslyn's and Breslow's mechanism for the buffer-catalyzed cleavage and isomerization of RNA phospho...
Scheme 5: General base-catalyzed cleavage of RNA phosphodiester bonds.
Scheme 6: Kirby´s mechanism for the buffer-catalyzed cleavage of RNA phosphodiester bonds [65].
Figure 7: Guanidinium-group-based cleaving agents of RNA.
Scheme 7: Tautomers of triazine-based cleaving agents and cleavage of RNA phosphodiester bonds by these agent...
Figure 8: Bifunctional guanidine/guanidinium group-based cleaving agents of RNA.
Scheme 8: Cleavage of HPNP by 1,3-distal calix[4]arene bearing two guanidine groups [80].
Figure 9: Cyclic amine-based cleaving agents of RNA.
Scheme 9: Mechanism for the pH-independent cleavage and isomerization of model compound 12a in the pH-range 7...
Scheme 10: Mechanism for the pH-independent cleavage of guanylyl-3´,3´-(2´-amino-2´-deoxyuridine) at pH 6-8 [89].
Scheme 11: Cleavage of uridine 3´-dimethyl phosphate by A) intermolecular attack of methoxide ion and B) intra...
Scheme 12: Transesterification of group I introns and hydrolysis of phosphotriester models proceed through a s...
Scheme 13: Cleavage of trinucleoside 3´,3´,5´-monophosphates by A) P–O3´ and B) P–O5´ bond fission.
Figure 10: Model compounds (23–25) and metal ion binding ligands used in kinetic studies of metal-ion-promoted...
Figure 11: Zn2+-ion-based mono- and di-nuclear cleaving agents of nucleic acids.
Figure 12: Miscellaneous complexes and ligands used in kinetic studies of metal-ion-promoted cleavage of nucle...
Figure 13: Azacrown ligands 34 and 35 and dinuclear Zn2+ complex 36 used in kinetic studies of metal-ion-promo...
Figure 14: Metal ion complexes used for determination of βlg values of metal-ion-promoted cleavage of RNA mode...
Figure 15: Metal ion complexes used in kinetic studies of medium effects on the cleavage of RNA model compound...
Scheme 14: Alternative mechanisms for metal-ion-promoted cleavage of phosphodiesters.
Figure 16: Nucleic acid cleaving agents where the attacking oxyanion is not coordinated to metal ion.
The synthesis of functionalized bridged polycycles via C–H bond insertion
- Jiun-Le Shih,
- Po-An Chen and
- Jeremy A. May
Beilstein J. Org. Chem. 2016, 12, 985–999, doi:10.3762/bjoc.12.97
- , even when the exocyclic oxygen was acetylated. This is likely related to the effects observed by Lee (Scheme 4). The Adams group also looked for a deuterium kinetic isotope effect for insertion in both 34 (Y = D, X = OMe) and 37 (Y = D, R = H). Only a small difference in relative rates between C–H and
- deuterium kinetic isotope effect of 2.34 was seen for C–H insertion with gold catalysis. Hashmi demonstrated the viability of dual gold catalysis for carbene/alkyne cascades with diynes like 109, which gave products from either a 1,2-methyl shift (not shown) or a C–H bond insertion to form enone 112 (Scheme
Graphical Abstract
Figure 1: Bridged polycyclic natural products.
Figure 2: Strategic limitations.
Scheme 1: Bridged rings from N–H bond insertions.
Scheme 2: The synthesis of deoxystemodin.
Scheme 3: A model system for ingenol.
Scheme 4: Formal synthesis of platensimycin.
Scheme 5: The formal synthesis of gerryine.
Scheme 6: Copper-catalyzed bridged-ring synthesis.
Scheme 7: Factors influencing insertion selectivity.
Scheme 8: Bridged-lactam formation.
Scheme 9: The total synthesis of (+)-codeine.
Scheme 10: A model system for irroratin.
Scheme 11: The utility of 1,6-insertion.
Scheme 12: Piperidine functionalization.
Scheme 13: Wilkinson’s catalyst for C–H bond insertion.
Scheme 14: Bridgehead insertion and the total synthesis of albene and santalene.
Scheme 15: The total synthesis of neopupukean-10-one.
Scheme 16: An approach to phomoidride B.
Scheme 17: Carbene cascade for fused bicycles.
Scheme 18: Cascade formation of bridged rings.
Scheme 19: Conformational effects.
Scheme 20: Hydrazone cascade reaction.
Scheme 21: Mechanistic studies.
Scheme 22: Gold carbene formation from alkynes.
Scheme 23: Au-catalyzed bridged-bicycle formation.
Scheme 24: Gold carbene/alkyne cascade.
Scheme 25: Gold carbene/alkyne cascade with C–H bond insertion.
Scheme 26: Platinum cascades.
Scheme 27: Tungsten cascade.
Cascade alkylarylation of substituted N-allylbenzamides for the construction of dihydroisoquinolin-1(2H)-ones and isoquinoline-1,3(2H,4H)-diones
- Ping Qian,
- Bingnan Du,
- Wei Jiao,
- Haibo Mei,
- Jianlin Han and
- Yi Pan
Beilstein J. Org. Chem. 2016, 12, 301–308, doi:10.3762/bjoc.12.32
- a cyclohexane radical-trapped compound (Scheme 5b). This implies that the current transformation is a radical process. Finally, an obvious competing kinetic isotope effect (KIE) was found with the ratio of 9.3:1 (kH:kD) when the reaction of 6a was performed with cyclohexane and [D]-cyclohexane
Graphical Abstract
Scheme 1: Cascade 1,2-difunctionalization and cyclization to construct heterocycles.
Scheme 2: Cyclization of cyclohexane (2a) with substituted N-(2-methylallyl)benzamide (reaction conditions: 4...
Scheme 3: Cyclization of cycloalkanes with N-methyl-N-(2-methylallyl)benzamide (reaction conditions: 4a (0.2 ...
Scheme 4: Cyclization reaction of 6 with cyclohexane 2a (reaction conditions: 6 (0.2 mmol), cyclohexane 2a (2...
Scheme 5: Control experiments for the mechanism studies. a) Reaction with N-unprotected substrate 8a; b) reac...
Scheme 6: Proposed mechanism.
Recent highlights in biosynthesis research using stable isotopes
- Jan Rinkel and
- Jeroen S. Dickschat
Beilstein J. Org. Chem. 2015, 11, 2493–2508, doi:10.3762/bjoc.11.271
- assembly of natural product. Also the kinetic isotope effect can be used to probe mechanistic proposals, as elegantly shown for the pentalenene (65) cyclization mechanism. Pentalenene synthase is one of the first and best investigated bacterial terpene cyclases both structurally [70] and functionally [71
Graphical Abstract
Figure 1: Structures of lovastatin (1), aflatoxin B1 (2) and amphotericin B (3).
Scheme 1: a) Structure of rhizoxin (4). b) Two possible mechanisms of chain branching catalysed by a branchin...
Scheme 2: Structure of coelimycin P1 (8) and proposed biosynthetic formation from the putative PKS produced a...
Scheme 3: Structure of trioxacarcin A (9) with highlighted carbon origins of the polyketide core from acetate...
Scheme 4: Proposed biosynthetic assembly of clostrubin A (12). Bold bonds show intact acetate units.
Figure 2: Structure of forazoline A (13).
Figure 3: Structures of tyrocidine A (14) and teixobactin (15).
Figure 4: Top: Structure of the NRPS product kollosin A (16) with the sequence N-formyl-D-Leu-L-Ala-D-Leu-L-V...
Scheme 5: Proposed biosynthesis of aspirochlorine (20) via 18 and 19.
Scheme 6: Two different macrocyclization mechanisms in the biosynthesis of pyrrocidine A (24).
Figure 5: Structure of thiomarinol A (27). Bold bonds indicate carbon atoms derived from 4-hydroxybutyrate.
Figure 6: Structures of artemisinin (28), ingenol (29) and paclitaxel (30).
Figure 7: The revised (31) and the previously suggested (32) structure of hypodoratoxide and the structure of...
Figure 8: Structure of the two interconvertible conformers of (1(10)E,4E)-germacradien-6-ol (34) studied with...
Scheme 7: Proposed cyclization mechanism of corvol ethers A (42) and B (43) with the investigated reprotonati...
Scheme 8: Predicted (top) and observed (bottom) 13C-labeling pattern in cyclooctatin (45) after feeding of [U-...
Scheme 9: Proposed mechanism of the cyclooctat-9-en-7-ol (52) biosynthesis catalysed by CotB2. Annotated hydr...
Scheme 10: Cyclization mechanism of sesterfisherol (59). Bold lines indicate acetate units; black circles repr...
Scheme 11: Cyclization mechanisms to pentalenene (65) and protoillud-6-ene (67).
Scheme 12: Reactions of chorismate catalyzed by three different enzyme subfamilies. Oxygen atoms originating f...
Scheme 13: Incorporation of sulfur into tropodithietic acid (72) via cysteine.
Scheme 14: Biosynthetic proposal for the starter unit of antimycin biosynthesis. The hydrogens at positions R1...
Pyridine-promoted dediazoniation of aryldiazonium tetrafluoroborates: Application to the synthesis of SF5-substituted phenylboronic esters and iodobenzenes
- George Iakobson,
- Junyi Du,
- Alexandra M. Z. Slawin and
- Petr Beier
Beilstein J. Org. Chem. 2015, 11, 1494–1502, doi:10.3762/bjoc.11.162
- aromatics using THF-d8 was reported [88]. We explain the reduced yield of 6-D (48% yield) and the formation of tar products by hydrogen atom abstraction from 3 or 6 and subsequent polymerization. No significant amounts of double deuterated products were detected. The kinetic isotope effect was determined
Graphical Abstract
Scheme 1: Borylation of aryldiazonium tetrafluoroborates 3. Reaction conditions: 3 (1 mmol), B2pin2 (1 mmol),...
Scheme 2: Proposed reaction mechanism.
Scheme 3: Reaction of diazonium salt 3i under borylation conditions.
Scheme 4: Suzuki–Miyaura reaction of boronates 2a and 2b with aryl iodides. Reaction conditions: 2 (1 mmol), ...
Scheme 5: Syntesis of boronic acid 8b and trifluoroborates 9. Reaction conditions for the synthesis of 8b: 2 ...
Scheme 6: Iodination of aryldiazonium tetrafluoroborates 3. Reaction conditions: 3 (1 mmol), I2 (1.1 mmol), p...
Synthesis of ethoxy dibenzooxaphosphorin oxides through palladium-catalyzed C(sp2)–H activation/C–O formation
- Seohyun Shin,
- Dongjin Kang,
- Woo Hyung Jeon and
- Phil Ho Lee
Beilstein J. Org. Chem. 2014, 10, 1220–1227, doi:10.3762/bjoc.10.120
- ranging from 50% and 63%. We carried out kinetic isotope effect (KIE) studies to prove the reaction mechanism (see Scheme 8). The required deuterium-labeled 2-(phenyl)phenylphosphonic acid monoethyl ester 1a-[D5] was efficiently prepared by a Suzuki reaction of deuterated bromobenzene (6) with 2
- PhI(OAc)2. However, no cyclized product was observed. This result indicates that the C–O reductive elimination from Pd(II) is not favorable. Because both the intermolecular and intramolecular competition experiments exhibited no significant kinetic isotope effect (kH/kD = 1.0 and 0.6; Scheme 8), we
Graphical Abstract
Scheme 1: Synthesis of alkoxy dibenzooxaphosphorin oxides by C(sp2)–H activation/C–O formation.
Scheme 2: Preparation of 2-(aryl)arylphosphonic acid monoethyl esters.
Scheme 3: A variety of organic acids and monoprotected amino acids as ligands.
Scheme 4: Cyclization of 2-arylphenylphosphonic acid monoethyl esters.
Scheme 5: Cyclization of 2-(aryl)arylphosphonic acid monoethyl esters.
Scheme 6: Preparation of 1a-[D5].
Scheme 7: Preparation of 1a-[D1].
Scheme 8: Studies with isotopically labelled compounds.
Scheme 9: A plausible mechanism.
[2H26]-1-epi-Cubenol, a completely deuterated natural product from Streptomyces griseus
- Christian A. Citron and
- Jeroen S. Dickschat
Beilstein J. Org. Chem. 2013, 9, 2841–2845, doi:10.3762/bjoc.9.319
- Streptomyces griseus. This compound represents the first completely deuterated terpene obtained by fermentation. Despite a few previous reports in the literature the operability of this approach to fully deuterated compounds is still surprising, because the strong kinetic isotope effect of deuterium is known
- eight to ten days of incubation until fully grown, reflecting the significantly slowed metabolism due to a strong deuterium kinetic isotope effect. After full growth of the culture the volatiles emitted by S. griseus were collected on charcoal traps by use of a closed-loop stripping apparatus (CLSA) [25
Graphical Abstract
Figure 1: Terpenoids from Streptomyces griseus.
Figure 2: Total ion chromatograms of CLSA headspace extracts from S. griseus obtained after (A) incubation on...
Figure 3: Mass spectra of 1-epi-cubenol. (A) Mass spectrum of natural 3 obtained after growth on 65.GYM; (B) ...
Figure 4: Ion chromatograms of fully deuterated 3 for (A) the molecular ion (m/z = 248, 247, and 246), and (B...
Recent advances in transition metal-catalyzed Csp2-monofluoro-, difluoro-, perfluoromethylation and trifluoromethylthiolation
- Grégory Landelle,
- Armen Panossian,
- Sergiy Pazenok,
- Jean-Pierre Vors and
- Frédéric R. Leroux
Beilstein J. Org. Chem. 2013, 9, 2476–2536, doi:10.3762/bjoc.9.287
- induction period and demonstrated the involvement of radical species in the reaction. The authors proposed a mechanism accounting for the EPR profile of the reaction and for the results of kinetic isotope effect experiments (Figure 21). In this mechanism, rhenium intervenes in the initiation step. It acts
Graphical Abstract
Scheme 1: Pd-catalyzed monofluoromethylation of pinacol phenylboronate [44].
Scheme 2: Cu-catalyzed monofluoromethylation with 2-PySO2CHFCOR followed by desulfonylation [49].
Scheme 3: Cu-catalyzed difluoromethylation with α-silyldifluoroacetates [57].
Figure 1: Mechanism of the Cu-catalyzed C–CHF2 bond formation of α,β-unsaturated carboxylic acids through dec...
Scheme 4: Fe-catalyzed decarboxylative difluoromethylation of cinnamic acids [62].
Scheme 5: Preliminary experiments for investigation of the mechanism of the C–H trifluoromethylation of N-ary...
Figure 2: Plausible catalytic cycle proposed by Z.-J. Shi et al. for the trifluoromethylation of acetanilides ...
Figure 3: Plausible catalytic cycle proposed by M. S. Sanford et al. for the perfluoroalkylation of simple ar...
Figure 4: Postulated reaction pathway for the Ag/Cu-catalyzed trifluoromethylation of aryl iodides by Z. Q. W...
Figure 5: Postulated reaction mechanism for Cu-catalyzed trifluoromethylation reaction using MTFA as trifluor...
Scheme 6: Formal Heck-type trifluoromethylation of vinyl(het)arenes by M. Sodeoka et al. [83].
Figure 6: Proposed catalytic cycle for the copper-catalyzed trifluoromethylation of (het)arenes in presence o...
Figure 7: Proposed catalytic cycle for the copper-catalyzed trifluoromethylation of N,N-disubstituted (hetero...
Figure 8: Proposed catalytic cycle by Y. Zhang and J. Wang et al. for the copper-catalyzed trifluoromethylati...
Figure 9: Mechanistic rationale for the trifluoromethylation of arenes in presence of Langlois’s reagent and ...
Scheme 7: Trifluoromethylation of 4-acetylpyridine with Langlois’s reagent by P. S. Baran et al. (* Stirring ...
Scheme 8: Catalytic copper-facilitated perfluorobutylation of benzene with C4F9I and benzoyl peroxide [90].
Figure 10: F.-L. Qing et al.’s proposed mechanism for the copper-catalyzed trifluoromethylation of (hetero)are...
Figure 11: Mechanism of the Cu-catalyzed/Ru-photocatalyzed trifluoromethylation and perfluoroalkylation of ary...
Figure 12: Proposed mechanism for the Cu-catalyzed trifluoromethylation of aryl- and vinyl boronic acids with ...
Figure 13: Possible mechanism for the Cu-catalyzed decarboxylative trifluoromethylation of cinnamic acids [62].
Scheme 9: Ruthenium-catalyzed perfluoroalkylation of alkenes and (hetero)arenes with perfluoroalkylsulfonyl c...
Figure 14: N. Kamigata et al.’s proposed mechanism for the Ru-catalyzed perfluoroalkylation of alkenes and (he...
Figure 15: Proposed mechanism for the Ru-catalyzed photoredox trifluoromethylation of (hetero)arenes with trif...
Figure 16: Late-stage trifluoromethylation of pharmaceutically relevant molecules with trifluoromethanesulfony...
Figure 17: Proposed mechanism for the trifluoromethylation of alkenes with trifluoromethyl iodide under Ru-bas...
Scheme 10: Formal perfluoroakylation of terminal alkenes by Ru-catalyzed cross-metathesis with perfluoroalkyle...
Figure 18: One-pot Ir-catalyzed borylation/Cu-catalyzed trifluoromethylation of complex small molecules by Q. ...
Figure 19: Mechanistic proposal for the Ni-catalyzed perfluoroalkylation of arenes and heteroarenes with perfl...
Scheme 11: Electrochemical Ni-catalyzed perfluoroalkylation of 2-phenylpyridine (Y. H. Budnikova et al.) [71].
Scheme 12: Fe(II)-catalyzed trifluoromethylation of arenes and heteroarenes with trifluoromethyl iodide (T. Ya...
Figure 20: Mechanistic proposal by T. Yamakawa et al. for the Fe(II)-catalyzed trifluoromethylation of arenes ...
Scheme 13: Ytterbium-catalyzed perfluoroalkylation of dihydropyran with perfluoroalkyl iodide (Y. Ding et al.) ...
Figure 21: Mechanistic proposal by A. Togni et al. for the rhenium-catalyzed trifluoromethylation of arenes an...
Figure 22: Mechanism of the Cu-catalyzed oxidative trifluoromethylthiolation of arylboronic acids with TMSCF3 ...
Scheme 14: Removal of the 8-aminoquinoline auxiliary [136].
Figure 23: Mechanism of the Cu-catalyzed trifluoromethylthiolation of C–H bonds with a trifluoromethanesulfony...
The role of silver additives in gold-mediated C–H functionalisation
- Scott R. Patrick,
- Ine I. F. Boogaerts,
- Sylvain Gaillard,
- Alexandra M. Z. Slawin and
- Steven P. Nolan
Beilstein J. Org. Chem. 2011, 7, 892–896, doi:10.3762/bjoc.7.102
- (Scheme 2) [16]. The observation of a high kinetic isotope effect is suggestive of a concerted metalation–deprotonation mechanism, as first suggested for Pd(II) complexes, in which a pivalate ligand behaves as a proton acceptor via a six-membered transition state [17]. However, addition via a transient Au
Graphical Abstract
Scheme 1: Silver-free C–H functionalisation using [Au(OH)(IPr)].
Scheme 2: C–H functionalisation of 2 using gold-phosphine complexes and a silver additive.
Figure 1: X-ray structure of [Au(OPiv)(IPr)] 3. Thermal ellipsoids are shown at the 50% probability level. H ...
Scheme 3: Carboxylation of 2 using 1 and Ag2O.
Catalysis: transition-state molecular recognition?
- Ian H. Williams
Beilstein J. Org. Chem. 2010, 6, 1026–1034, doi:10.3762/bjoc.6.117
- an archetypal reaction in organic chemistry and an important process in biochemistry. Catechol-O-methyl transferase (COMT) catalyses methyl transfer from S-adenosylmethionine (SAM) to a catechol (Scheme 1), and this reaction manifests an unusually large inverse secondary kinetic isotope effect as
Graphical Abstract
Figure 1: Free energy profiles for reactions of substrate S uncatalysed and catalysed by enzyme E, showing ho...
Scheme 1: SN2 methyl transfer from SAM to catechol catalysed by COMT.
Figure 2: Energetic analysis of the compression hypothesis for enzyme-catalysed methyl transfer.
Figure 3: Catalyst design for methyl transfer: (a) the reaction to be catalysed; (b) dipoles favourably align...
Scheme 2: SN2 methyl transfer (a) uncatalysed and (b) within a cryptand cavity.
Figure 4: Free energy analysis of COMT catalysis.
Scheme 3: Formation of glycosyl-enzyme covalent intermediate COV.
Figure 5: Conformational change of the xylose ring from chair (via envelope) with long OYHY…Oring hydrogen bo...
Figure 6: AM1/OPLS potentials of mean force for formation of glycosyl-enzyme covalent intermediate between 4-...
Figure 7: Hydrogen-bond distances HY…Oring (red) and HY…Onuc (blue) to boat conformer of RC, TS and glycosyl-...
