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Search for "reductive dimerization" in Full Text gives 9 result(s) in Beilstein Journal of Organic Chemistry.
N-Glycosides of indigo, indirubin, and isoindigo: blue, red, and yellow sugars and their cancerostatic activity
- Peter Langer
Beilstein J. Org. Chem. 2024, 20, 2840–2869, doi:10.3762/bjoc.20.240
- ‘-diglycosides In our group, the synthesis of N,N’-diglycosylated isoindigos was studied. In contrast to isatin-N-glycosides, oxindole-N-glycosides are not readily available. Therefore, reductive dimerization of isatin-N-glycosides was considered as a strategy for the synthesis of the target compounds. Isatin-N
Graphical Abstract
Scheme 1: Structures of indigo (1a), indirubin (2a) and isoindigo (3a).
Scheme 2: Structures of akashins A–C.
Scheme 3: Synthesis of 5b. Reagents and conditions: i) TMSOTf, 4 Å MS, CH2Cl2, −20 °C, 1.5 h, then 20 °C, 8–1...
Scheme 4: Synthesis of 7c. Reagents and conditions: i) TMSOTf, 4 Å MS, CH2Cl2, −18 °C, 3 h; then: TMSOTf, 4 Å...
Scheme 5: Synthesis of 1d. Reagents and conditions: i) chloroacetic acid, Na2CO3, reflux, 6 h; ii) Ac2O, NaOA...
Scheme 6: Synthesis of 10e. Reagents and conditions: i) p-TsOH·H2O, acetonitrile, MeOH, 1 d; ii) NIS, PPh3, D...
Scheme 7: Synthesis of akashins A–C. Reagents and conditions: i) TMSOTf, 4 Å MS, CH2Cl2, −18 to 20 °C, 15 h; ...
Scheme 8: Synthesis of 5d. Reagents and conditions: i) KMnO4, AcOH, high-power-stirring (12.000 rot/min), 20 ...
Scheme 9: Possible mechanism of the formation of 5c.
Scheme 10: Synthesis of 7d. Reagents and conditions: i) 1) CH2Cl2, 2) Me3SiI, 20 °C, 30 min, 3) 0 °C, 30 min, ...
Scheme 11: Synthesis of α-15b. Reagents and conditions: i) 1) CH2Cl2, 2) Me3SiI, 20 °C, 30 min, 3) 0 °C, 30 mi...
Scheme 12: Synthesis of isatin-N-glycosides 16a–f. Reagents and conditions: i) PhNH2, EtOH, 20 °C, 12 h; ii) Ac...
Scheme 13: Synthesis of 17–21. Reagents and conditions: i) Na2CO3, MeOH, 20 °C, 4 h.
Scheme 14: Synthesis of indirubin-N-glycosides α-17a and α-17b.
Scheme 15: Synthesis of β-17f. Reagents and conditions: i) 1) Na2CO3, MeOH, 20 °C, 4 h, 2) Ac2O/pyridine 1:1, ...
Scheme 16: Synthesis of β-24a. Reagents and conditions: i) n-PrOH, H2O, formic acid (buffer, 100 mM), 2 h, 65 ...
Scheme 17: Synthesis of isatin-N-glycosides 23b–g and 24b–g.
Scheme 18: Synthesis of β-29a,b. Reagents and conditions: i) EtOH, 20 °C, 12 h; ii) DDQ, dioxane, 20 °C, 12 h;...
Scheme 19: Synthesis of β-31a. Reagents and conditions: i) Na2SO3, dioxane, H2O, 110 °C, 2 d; ii) piperidine, ...
Scheme 20: Synthesis of 33a–d. Reagents and conditions: i) Ac2O, AcOH, NaOAc, 80 °C, 1 h; ii) 1) NaOMe, anhydr...
Scheme 21: Indirubins 34 and 35.
Scheme 22: Synthesis of 36f. Reagents and conditions: i) NaOH, H2O, 20 °C, 5 h; ii) HCl, NaNO2, H2O, −14 °C; i...
Scheme 23: Synthesis of 38a–h. Reagents and conditions: i) 1) 0.1 equiv NaOMe, MeOH, 20 °C, 15–20 min, 2) HOAc...
Scheme 24: Synthesis of 40a–h. Reagents and conditions: i) method A: EtOH/THF, cat. KOt-Bu, 20 °C, 3–4.5 h; me...
Scheme 25: Synthesis of 41a–d. Reagents and conditions: i) Ac2O, AcOH, NaOAc, 80 °C, 1 h.
Scheme 26: Synthesis of 41e. Reagents and conditions: i) AcOH, NaOAc, 110 °C, 24 h.
Scheme 27: Synthesis of E-β-43a–e and E-β-44a,b. Reagents and conditions: i) 1) NEt3, EtOH, 20 °C, 12 h, 2) DM...
Scheme 28: Synthesis of E-43f. Reagents and conditions: i) Na2CO3, MeOH, 20 °C, 6–24 h.
Scheme 29: Synthesis of 46a–m. Reagents and conditions: i) NEt3 (1 equiv), EtOH, 20 °C, 6–10 h; ii) MsCl, NEt3...
Scheme 30: Synthesis of 48a–d. Reagents and conditions: i) AcOH/Ac2O, NaOAc, 60 °C, 3–4 h.
Scheme 31: Synthesis of 48e. Reagents and conditions: i) NaOAc, AcOH, 110 °C, 24 h.
Scheme 32: Synthesis of β-49a,b. Reagents and conditions: i) AcOH/Ac2O, NaOAc, 60 °C, 3–4 h.
Scheme 33: Synthesis of β-54a,b. Reagents and conditions: i) 1) NaH, DMF, 0 °C, 15 min, 2) β-51a,b, 20 °C, 3 h...
Scheme 34: Synthesis of 54c–l. The yields refer to the yields of the first and second condensation step for ea...
Scheme 35: Synthesis of 57a–c and 58a–d. Reagents and conditions: i) HCl (conc.), AcOH, reflux, 24 h; ii) 1) B...
Scheme 36: Synthesis of 59a–e and 60a–e. Reagents and conditions: i) P(NEt2)3 (1.1 equiv), CH2Cl2, −78 °C to 2...
Scheme 37: Synthesis of 61a–d and 62a–d. Reagents and conditions: i) P(NEt2)3 (1.1 equiv), CH2Cl2, −78 °C to 2...
Scheme 38: Synthesis of β-64a–e and α-64a. Reagents and conditions: i) AcOH, Ac2O, NaOAc, 90 °C, 6 h.
Scheme 39: Synthesis of β-72a. Reagents and conditions: i) 66, EtOH, 20 °C, 12 h; ii) DDQ, dioxane, 20 °C, 12 ...
Scheme 40: Synthesis of β-72b.
Scheme 41: Synthesis of β-74a–c. Reagents and conditions: i) AcOH, Ac2O, NaOAc, 130 °C, 2 d.
Scheme 42: Synthesis of β-77. Reagents and conditions: i) 1) NEt3, EtOH, 20 °C, 12 h, 2) DMAP, NEt3, MsCl, 0 °...
Scheme 43: Synthesis of β-81a–f and β-80g. Reagents and conditions: i) AcOH, 80 °C, 1–3 h; ii) benzene, PTSA, ...
Scheme 44: Synthesis of 84a. Reagents and conditions: i) benzene, AlCl3, 20 °C, 10 min; ii) MeOH, NaOMe, 12 h,...
Scheme 45: Synthesis of 84b–l. The yields refer to the yields of the condensation and the deprotection step fo...
Beyond n-dopants for organic semiconductors: use of bibenzo[d]imidazoles in UV-promoted dehalogenation reactions of organic halides
- Kan Tang,
- Megan R. Brown,
- Chad Risko,
- Melissa K. Gish,
- Garry Rumbles,
- Phuc H. Pham,
- Oana R. Luca,
- Stephen Barlow and
- Seth R. Marder
Beilstein J. Org. Chem. 2023, 19, 1912–1922, doi:10.3762/bjoc.19.142
- ; reduction; reductive dimerization; Introduction Reductive dehalogenation reactions of organic halides can be used in organic synthesis as a means of generating carbon-centered radical or anion intermediates and could have relevance to the treatment of waste halogenated polymers. While such reactions can be
- -containing catalysts [32]. We note that another all-organic reductive dimerization of benzyl halides using 2,3,5,6-tetrakis(tetramethylguanidino)pyridine has recently been reported [37]. The less readily reduced halides examined here (1d,e, and 2) are only sluggishly converted, even when using both (N-DMBI)2
Graphical Abstract
Figure 1: (a, b) Schematics of previous approaches to dehalogenation-based reactions using molecular reductan...
Scheme 1: Selective deiodination of 2-iodobenzyl chloride.
Scheme 2: Reaction mechanisms for the reactions of dimeric reductants (D2) such as (Y-DMBI)2 derivatives with...
Figure 2: (a) A representative temporal evolution of % conversion (blue squares), % toluene yield (red diamon...
Figure 3: Top: UV–vis absorption spectra for the two dimeric reductants in THF emphasizing (a) the different ...
Figure 4: Transient absorption spectra of (a) (N-DMBI)2 in MeCN, (b) (N-DMBI)2 in toluene, and (c) (Cyc-DMBI)2...
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.
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
- catalyst in the reductive dimerization of aryl olefins 32 reported by van der Donk in 2002 [71]. This group showed the formation of a new C–C bond between benzylic carbons, affording compounds 33 with two vicinal quaternary carbon centers (Scheme 17). The occurrence of a radical pathway was proposed based
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]).
Pd(OAc)2/Ph3P-catalyzed dimerization of isoprene and synthesis of monoterpenic heterocycles
- Dominik Kellner,
- Maximilian Weger,
- Andrea Gini and
- Olga García Mancheño
Beilstein J. Org. Chem. 2017, 13, 1807–1815, doi:10.3762/bjoc.13.175
- system PdBr2(dppe)/NaOPh/PhOH [31]. Furthermore, an interesting work by Heck and co-workers in 1976 already showed the possibility of generating the corresponding dimethyloctadienes of isoprene by a reductive dimerization in the presence of formic acid with the dimeric allylpalladium acetate catalyst and
Graphical Abstract
Figure 1: Isoprene as chemical building block in nature and organic synthesis.
Scheme 1: Pd-catalyzed dimerization of isoprene.
Scheme 2: Putative mechanism for the Pd(OAc)2-catalyzed dimerization of isoprene.
Scheme 3: Functionalization of the isoprene-dimer 2-TT to substituted O- and N-heterocycles.
SmI2-mediated dimerization of indolylbutenones and synthesis of the myxobacterial natural product indiacen B
- Nils Marsch,
- Peter G. Jones and
- Thomas Lindel
Beilstein J. Org. Chem. 2015, 11, 1700–1706, doi:10.3762/bjoc.11.184
- -configuration were formed by SmI2-mediated reductive dimerization of a 4-(indol-6-yl)butenone, obtained by Heck reaction. The two indolyl units appear to chelate Sm(II)/(III) leading to a gauche-type arrangement at the newly formed bond between the two β-carbons. Through a sequence of Sonogashira cross coupling
- their reductive dimerization. We also describe the synthesis of the antimicrobial natural product indiacen B (2) from the myxobacterium Sandaracinus amylolyticus [5], bearing a unique isoprene moiety chlorinated at the methylene group. Results and Discussion SmI2-induced reductive dimerizations 6
- had been obtained in the case of intramolecular reactions where the β-positions of the enone systems were covalently tethered. Shinohara et al. have also reported a reductive dimerization of methyl cinnamate resulting in a cis-orientation of the phenyl rings [25]. SmI2-induced reductive dimerization
Graphical Abstract
Figure 1: Prenylated indole alkaloids raputindole A from the rutaceous tree Raputia simulans and indiacen B f...
Scheme 1: Synthesis and SmI2-mediated reductive dimerization of natural product 5.
Scheme 2: Model visualizing the stereochemical course of the cyclopentanol formation leading to product 6. Po...
Scheme 3: Meyer–Schuster rearrangement of 13 and SmI2-mediated reductive [3 + 2] cycloaddition, followed by e...
Scheme 4: Nazarov-type cyclization of 14 to cyclopentanones 17 and 18; synthesis of verticillatine B (20).
Scheme 5: Synthesis and X-ray analysis of indiacen B (2, ORTEP drawing with ellipsoides at 50% probability).
Cathodic hydrodimerization of nitroolefins
- Michael Weßling and
- Hans J. Schäfer
Beilstein J. Org. Chem. 2015, 11, 1163–1174, doi:10.3762/bjoc.11.131
- reduction of the nitro group to oximes would be favoured. On the other side the electrolyte should not be aprotic as protons are required for protonation of the intermediate anions in the reductive dimerization (Scheme 1). According to the proposed mechanism for the cathodic hydrodimerization the radical
- in [6][7][8]. There have been reports on the reductive dimerization of nitro alkenes prior to 1991. 1,4-Dinitro-2,3-diphenylbutane (3) has been obtained in less than 20% yield in the catalytic hydrogenation of β-nitrostyrene (4) [11]. Hydrodimerization of 4 was observed in enzymatic reduction [12
Graphical Abstract
Scheme 1: Proposed mechanisms via pathways (I) to (III) for the cathodic hydrodimerization of olefins with el...
Scheme 2: Cathodic reduction of nitroalkene 1 to hydrodimer 2 and oxime 5.
Scheme 3: Preparation of the 1-aryl-2-nitroalkenes 1, 4, 8–15.
Scheme 4: Reduction potentials (Ep,c in Volt) of nitroolefins. Conditions: amalgamated gold wire, v = 0.1 V/s...
Figure 1: (a) CV of 15; v = 0.1 V/s, (b) CV of 15; v = 10 V/s.
Scheme 5: Hydrodimerization of nitroalkene 14 and 15.
Scheme 6: (a) Intramolecular hydrocoupling of dinitrodiene 16 and (b) hydrodimerization of 1-nitrocyclohexene...
Scheme 7: Possible stereoisomers and their mirror images for the hydrodimers 2 and 18–23; R and S are the con...
Figure 2: 1H NMR spectrum of 18b (without aromatic H); below experimental spectrum, above: simulated signals ...
Cathodic reductive coupling of methyl cinnamate on boron-doped diamond electrodes and synthesis of new neolignan-type products
- Taiki Kojima,
- Rika Obata,
- Tsuyoshi Saito,
- Yasuaki Einaga and
- Shigeru Nishiyama
Beilstein J. Org. Chem. 2015, 11, 200–203, doi:10.3762/bjoc.11.21
- . As shown in Figure 1, the radical intermediate derived from phenylacrylate through a one-electron reduction (right) differs from that obtained by anodic oxidation of 4-hydroxyphenyl-1-propene (left). Therefore, the reductive dimerization of cinnamic acid derivatives was expected to provide access to
Graphical Abstract
Figure 1: Expected coupling products from one-electron oxidation (left) and one-electron reduction (right) of...
Scheme 1: Chemical conversion of (±)-2 into E-5 and E-8.
An improved procedure for the preparation of Ru(bpz)3(PF6)2 via a high-yielding synthesis of 2,2’-bipyrazine
- Danielle M. Schultz,
- James W. Sawicki and
- Tehshik P. Yoon
Beilstein J. Org. Chem. 2015, 11, 61–65, doi:10.3762/bjoc.11.9
- bpz have been reported [26][27][28], the most common of which involve transition metal-catalyzed reductive homocouplings of halopyrazine electrophiles [29][30]. However, we found these procedures to be capricious in our hands, and after a survey of known reductive dimerization protocols, the highest
Graphical Abstract
Figure 1: Influence of ligand structure on photoredox behavior.
Scheme 1: Pd-catalyzed reductive coupling of 2-chloropyrazine.
Scheme 2: Preparative-scale synthesis of Ru(bpz)3(PF6)2.
