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Search for "SN2' reaction" in Full Text gives 57 result(s) in Beilstein Journal of Organic Chemistry.
One-pot sequential synthesis of isocyanates and urea derivatives via a microwave-assisted Staudinger–aza-Wittig reaction
- Diego Carnaroglio,
- Katia Martina,
- Giovanni Palmisano,
- Andrea Penoni,
- Claudia Domini and
- Giancarlo Cravotto
Beilstein J. Org. Chem. 2013, 9, 2378–2386, doi:10.3762/bjoc.9.274
- undesired side-product formation and, consequently, a lower yield. Therefore, the choice of the right solvent and reaction conditions is the key to the success of this transformation. Our initial attempts focused on the synthesis of azido derivatives in MeCN. Although generally performed in DMF, the SN2
- reaction of alkyl bromide with NaN3 can also be performed in MeCN. NaN3 is insoluble in MeCN at room temperature (<0.005 g/100 mL), but its solubility increases at higher temperatures. Furthermore, NaBr generated during the nucleophilic substitution is insoluble and can be removed by filtration as can the
Kinetics and mechanism of the anilinolysis of aryl phenyl isothiocyanophosphates in acetonitrile
- Hasi Rani Barai and
- Hai Whang Lee
Beilstein J. Org. Chem. 2013, 9, 615–620, doi:10.3762/bjoc.9.68
- congestion in the bond-making process in a stepwise process with a rate-limiting bond formation (or a normal SN2 reaction) [13][14][15]. The magnitudes of the kH/kD values invariably decrease as the aniline becomes less basic. The magnitudes of the kH/kD values invariably increase for X = (4-MeO, 4-Me, H, 4
Graphical Abstract
Scheme 1: Reactions of Y-aryl phenyl isothiocyanophosphates (1a–e) with XC6H4NH2(D)2 in MeCN at 55.0 °C.
Figure 1: Brönsted plots with X [log kH versus pKa(X)] of the reactions of Y-aryl phenyl isothiocyanophosphat...
Figure 2: Plots of ρX versus σY and ρY versus σX of the reactions of Y-aryl phenyl isothiocyanophosphates wit...
Scheme 2: Backside attack involving in-line-type TSb and frontside attack involving a hydrogen-bonded, four-c...
Scheme 3: Backside attack involving a hydrogen-bonded, four-center-type TSb-H.
The chemistry of bisallenes
- Henning Hopf and
- Georgios Markopoulos
Beilstein J. Org. Chem. 2012, 8, 1936–1998, doi:10.3762/bjoc.8.225
- coming close to a general route to introduce functionality into bisallenes at the present time seems to be the double SN2'-reaction of 2,4-hexadiyne-1,6-diol (63, e.g. R1 to R4 = aryl) and its derivatives with various nucleophiles (Scheme 13) [49][50]. Thus, heating the diols 63 with an aromatic or
Graphical Abstract
Figure 1: Loschmidt’s structure proposal for benzene (1) (Scheme 181 from [3]) and the corresponding modern stru...
Figure 2: The first isolated bisallenes.
Figure 3: Carbon skeletons of selected bisallenes discussed in this review.
Scheme 1: The preparation of 1,2,4,5-hexatetraene (2).
Scheme 2: The preparation of a conjugated bisallene by the DMS-protocol.
Scheme 3: Preparation of the 3-deuterio- and 3,4-dideuterio derivatives of 24.
Scheme 4: A versatile method to prepare alkylated conjugated bisallenes and other allenes.
Scheme 5: A preparation of 3,4-dimethyl-1,2,4,5-hexatetraene (38).
Scheme 6: A (C6 + 0)-approach to 1,2,4,5-hexatetraene (2).
Scheme 7: The preparation of a fully alkylated bisallenes from a 2,4-hexadiyne-1,6-diol diacetate.
Scheme 8: The preparation of the first phenyl-substituted conjugated bisallenes 3 and 4.
Scheme 9: Selective hydrogenation of [5]cumulenes to conjugated bisallenes: another (C6 + 0)-route.
Scheme 10: Aryl-substituted conjugated bisallenes by a (C3 + C3)-approach.
Scheme 11: Hexaphenyl-1,2,4,5-hexatetraene (59) by a (C3 + C3)-approach.
Scheme 12: An allenation route to conjugated bisallenes.
Scheme 13: The preparation of 3,4-difunctionalized conjugated bisallenes.
Scheme 14: Problems during the preparation of sulfur-substituted conjugated bisallenes.
Scheme 15: The preparation of 3,4-dibromo bisallenes.
Scheme 16: Generation of allenolates by an oxy-Cope rearrangement.
Scheme 17: A linear trimerization of alkynes to conjugated bisallenes: a (C2 + C2 + C2)-protocol.
Scheme 18: Preparation of a TMS-substituted conjugated bisallene by a C3-dimerization route.
Scheme 19: A bis(trimethylsilyl)bisallene by a C3-coupling protocol.
Scheme 20: The rearrangement of highly substituted benzene derivatives into their conjugated bisallenic isomer...
Scheme 21: From fully substituted benzene derivatives to fully substituted bisallenes.
Scheme 22: From a bicyclopropenyl to a conjugated bisallene derivative.
Scheme 23: The conversion of a bismethylenecyclobutene into a conjugated bisallene.
Scheme 24: The preparation of monofunctionalized bisallenes.
Scheme 25: Preparation of bisallene diols and their cyclization to dihydrofurans.
Scheme 26: A 3,4-difunctionalized conjugated bisallene by a C3-coupling process.
Scheme 27: Preparation of a bisallenic diketone by a coupling reaction.
Scheme 28: Sulfur and selenium-substituted bisallenes by a [2.3]sigmatropic rearrangement.
Scheme 29: The biallenylation of azetidinones.
Scheme 30: The preparation of a fully ferrocenylated conjugated bisallene.
Scheme 31: The first isomerization of a 1,5-hexadiyne to a 1,2,4,5-hexatetraene.
Scheme 32: The preparation of alkynyl-substituted bisallenes by a C3-dimerization protocol.
Scheme 33: Preparation of another completely ferrocenylated bisallene.
Scheme 34: The cyclization of 1,5-hexadiyne (129) to 3,4-bismethylenecyclobutene (130) via 1,2,4,5-hexatetraen...
Scheme 35: Stereochemistry of the thermal cyclization of bisallenes to bismethylenecyclobutenes.
Scheme 36: Bisallene→bismethylenecyclobutene ring closures in the solid state.
Scheme 37: A bisallene cyclization/dimerization reaction.
Scheme 38: A selection of Diels–Alder additions of 1,2,4,5-hexatetraene with various double-bond dienophiles.
Scheme 39: The stereochemistry of the [2 + 4] cycloaddition to conjugated bisallenes.
Scheme 40: Preparation of azetidinone derivatives from conjugated bisallenes.
Scheme 41: Cycloaddition of heterodienophiles to a conjugated bisallene.
Scheme 42: Addition of triple-bond dienophiles to conjugated bisallenes.
Scheme 43: Sulfur dioxide addition to conjugated bisallenes.
Scheme 44: The addition of a germylene to a conjugated bisallene.
Scheme 45: Trapping of conjugated bisallenes with phosphinidenes.
Scheme 46: The cyclopropanantion of 1,2,4,5-hexatetraene (2).
Scheme 47: Photochemical reactions involving conjugated bisallenes.
Scheme 48: Base-catalyzed isomerizations of conjugated bisallenes.
Scheme 49: Ionic additions to a conjugated bisallene.
Scheme 50: Oxidation reactions of a conjugated bisallene.
Scheme 51: The mechanism of oxidation of the bisallene 24.
Scheme 52: CuCl-catalyzed cyclization of 1,2,4,5-hexatetraene (2).
Scheme 53: The conversion of conjugated bisallenes into cyclopentenones.
Scheme 54: Oligomerization of a conjugated bisallene by nickel catalysts.
Scheme 55: Generation of 1,2,5,6-heptatetraene (229) as a reaction intermediate.
Scheme 56: The preparation of a stable derivative of 1,2,5,6-heptatetraene.
Scheme 57: A bisallene with a carbonyl group as a spacer element.
Scheme 58: The first preparation of 1,2,6,7-octatetraene (242).
Scheme 59: Preparation of 1,2,6,7-octatetraenes by (C4 + C4)-coupling of enynes.
Scheme 60: Preparation of 1,2,6,7-octatetraenes by (C4 + C4)-coupling of homoallenyl bromides.
Scheme 61: Preparation of 1,2,6,7-octatetraenes by alkylation of propargylic substrates.
Scheme 62: Preparation of two highly functionalized 1,2,6,7-octatetraenes.
Scheme 63: Preparation of several higher α,ω-bisallenes.
Scheme 64: Preparation of different alkyl derivatives of α,ω-bisallenes.
Scheme 65: The preparation of functionalized 1,2,7,8-nonatetraene derivatives.
Scheme 66: Preparation of functionalized α,ω-bisallenes.
Scheme 67: The preparation of an α,ω-bisallene by direct homologation of an α,ω-bisalkyne.
Scheme 68: The gas-phase pyrolysis of 4,4-dimethyl-1,2,5,6-heptatetraene (237).
Scheme 69: Gas-phase pyrolysis of 1,2,6,7-octatetraene (242).
Scheme 70: The cyclopropanation of 1,2,6,7-octatetraene (242).
Scheme 71: Intramolecular cyclization of 1,2,6,7-octatetraene derivatives.
Scheme 72: The gas-phase pyrolysis of 1,2,7,8-nonatetraene (265) and 1,2,8,9-decatetraene (266).
Scheme 73: Rh-catalyzed cyclization of a functionalized 1,2,7,8-nonatetraene.
Scheme 74: A triple cyclization involving two different allenic substrates.
Scheme 75: Bicyclization of keto derivatives of 1,2,7,8-nonatetraene.
Scheme 76: The preparation of complex organic compounds from functionalized bisallenes.
Scheme 77: Cycloisomerization of an α,ω-bisallene containing a C9 tether.
Scheme 78: Organoborane polymers from α,ω-bisallenes.
Scheme 79: Preparation of trans- (337) and cis-1,2,4,6,7-octapentaene (341).
Scheme 80: The preparation of 4-methylene-1,2,5,6-heptatetraene (349).
Scheme 81: The preparation of acetylenic bisallenes.
Scheme 82: The preparation of derivatives of hydrocarbon 351.
Scheme 83: The construction of macrocyclic alleno-acetylenes.
Scheme 84: Preparation and reactions of 4,5-bismethylene-1,2,6,7-octatetraene (365).
Scheme 85: Preparation of 1,2-bis(propadienyl)benzene (370).
Scheme 86: The preparation of 1,4-bis(propadienyl)benzene (376).
Scheme 87: The preparation of aromatic and heteroaromatic bisallenes by metal-mediated coupling reactions.
Scheme 88: Double cyclization of an aromatic bisallene.
Scheme 89: Preparation of an allenic [15]paracyclophane by a ring-closing metathesis reaction of an aromatic α...
Scheme 90: Preparation of a macrocyclic ring system containing 1,4-bis(propadienyl)benzene units.
Scheme 91: Preparation of copolymers from 1,4-bis(propadienyl)benzene (376).
Scheme 92: A boration/copolymerization sequence of an aromatic bisallene and an aromatic bisacetylene.
Scheme 93: Formation of a layered aromatic bisallene.
Figure 4: The first members of the semicyclic bisallene series.
Scheme 94: Preparation of the first bis(vinylidene)cyclobutane derivative.
Scheme 95: Dimerization of strain-activated cumulenes to bis(vinylidene)cyclobutanes.
Scheme 96: Photodimerization of two fully substituted butatrienes in the solid state.
Scheme 97: Preparation of the two parent bis(vinylidene)cyclobutanes.
Scheme 98: The preparation of 1,3-bis(vinylidene)cyclopentane and its thermal isomerization.
Scheme 99: The preparation of the isomeric bis(vinylidene)cyclohexanes.
Scheme 100: Bi- and tricyclic conjugated bisallenes.
Scheme 101: A selection of polycyclic bisallenes.
Scheme 102: The first endocyclic bisallenes.
Figure 5: The stereochemistry of 1,2,6,7-cyclodecatetraene.
Scheme 103: The preparation of several endocyclic bisallenes.
Scheme 104: Synthesis of diastereomeric derivatives of 1,2,6,7-cyclodecatetraene.
Scheme 105: Preparation of a derivative of 1,2,8,9-cyclotetradecatetraene.
Scheme 106: The preparation of keto derivatives of cyclic bisallenes.
Scheme 107: The preparation of cyclic biscumulenic ring systems.
Scheme 108: Cyclic bisallenes in natural- and non-natural-product chemistry.
Scheme 109: The preparation of iron carbonyl complexes from cyclic bisallenes.
Figure 6: A selection of unknown exocyclic bisallenes that should have interesting chemical properties.
Scheme 110: The thermal isomerization of 1,2-diethynylcyclopropanes and -cyclobutanes.
Scheme 111: Intermediate generation of a cyclooctapentaene.
Scheme 112: Attempted preparation of a cyclodecahexaene.
Scheme 113: The thermal isomerization of 1,5,9-cyclododecatriyne (511) into [6]radialene (514).
Scheme 114: An isomerization involving a diketone derived from a conjugated bisallene.
Scheme 115: Typical reaction modes of heteroorganic bisallenes.
Scheme 116: Generation and thermal behavior of acyclic hetero-organic bisallenes.
Scheme 117: Generation of bis(propadienyl)thioether.
Scheme 118: The preparation of a bisallenic sulfone and its thermal isomerization.
Scheme 119: Bromination of the bisallenic sulfone 535.
Scheme 120: Metalation/hydrolysis of the bisallenic sulfone 535.
Scheme 121: Aromatic compounds from hetero bisallenes.
Scheme 122: Isomerization/cyclization of bispropargylic ethers.
Scheme 123: The preparation of novel aromatic systems by base-catalyzed isomerization of bispropargyl ethers.
Scheme 124: The isomerization of bisacetylenic thioethers to bicyclic thiophenes.
Scheme 125: Aromatization of macrocyclic bispropargylic sulfides.
Scheme 126: Preparation of ansa-compounds from macrocyclic bispropargyl thioethers.
Scheme 127: Alternate route for cyclization of a heterorganic bisallene.
Scheme 128: Multiple isomerization/cyclization of “double” bispropargylic thioethers.
Scheme 129: Preparation of a bisallenyl disulfide and its subsequent bicyclization.
Scheme 130: Thermal cyclization of a bisallenyl thiosulfonate.
Scheme 131: Some reactions of heteroorganic bisallenes with two sulfur atoms.
Scheme 132: Further methods for the preparation of heteroorganic bisallenes.
Scheme 133: Cyclization reactions of heteroorganic bisallenes.
Scheme 134: Thermal cycloadditions of bisallenic tertiary amines.
Scheme 135: Cyclization of a bisallenic tertiary amine in the presence of a transition-metal catalyst.
Scheme 136: A Pauson–Khand reaction of a bisallenic ether.
Scheme 137: Formation of a 2:1adduct from two allenic substrates.
Scheme 138: A ring-forming silastannylation of a bisallenic tertiary amine.
Scheme 139: A three-component cyclization involving a heterorganic bisallene.
Scheme 140: Atom-economic construction of a complex organic framework from a heterorganic α,ω-bisallene.
Alkene selenenylation: A comprehensive analysis of relative reactivities, stereochemistry and asymmetric induction, and their comparisons with sulfenylation
- Vadim A. Soloshonok and
- Donna J. Nelson
Beilstein J. Org. Chem. 2011, 7, 744–758, doi:10.3762/bjoc.7.85
- ]. It is well established that the rate determining step in benzenesulfenyl chloride addition is the formation of thiiranium intermediate; specifically the alkene π electrons displace Cl− in an SN2 reaction to give the thiiranium ion [89]. On the other hand, recent studies ruled out the formation of the
Graphical Abstract
Figure 1: Chiral aryl selenium electrophiles 1–3.
Scheme 1: Plausible mechanism of alkene selenenylation.
Figure 2: Plot of log krel values for PhSeCl addition to alkenes versus their corresponding IEs. Point number...
Figure 3: Plot of log krel values for PhSeCl addition to alkenes versus their corresponding HOMOs, analogous ...
Figure 4: Plot of log krel versus HOMO shows data grouped by branching at α position. Data are from Table 3; point n...
Scheme 2: Major products from reactions of 1 and 2 with representative alkenols.
Figure 5: Structure of intermediate complex 9.
Figure 6: Plot of log krel values for PhSCl addition to alkenes versus their IEs. Data are from Table 6.
Asymmetric synthesis of tertiary thiols and thioethers
- Jonathan Clayden and
- Paul MacLellan
Beilstein J. Org. Chem. 2011, 7, 582–595, doi:10.3762/bjoc.7.68
- the preparation of certain families of tertiary thiols and thioethers. For example, SN2 displacement of a mesylate leaving group by thiophenol can be accomplished using α-hydroxy esters 2 (Scheme 1) [12]. The presence of the α-ester group of 3 promotes SN2 reaction in two ways: The electron
- cyanohydrins, can also be made to undergo SN2 reaction with sulfur nucleophiles [13]. However, substitution of the quaternary α-(sulfonyloxy)nitrile 11 is very slow, and conversion of 11 to 12 with potassium thioacetate in DMF proceeds in only 35% yield after 72 hours. SN2 displacement of the leaving group by
Graphical Abstract
Figure 1: Seven out of the ten top selling drugs in the USA in 2009 contain sulfur. Figures in italics are to...
Figure 2: Naturally occurring organosulfur compounds glutathione and (R)-thioterpineol.
Figure 3: Methods for the synthesis of chiral tertiary thiol 1.
Scheme 1: Preparation of thioethers 4 from α-hydroxy esters.
Scheme 2: Nucleophilic substitution in α-aryl-α-hydroxy esters.
Scheme 3: Preparation of α,α-dialkylthioethers.
Scheme 4: Preparation of α-cyanothioacetate 12.
Scheme 5: Synthesis of (R)-(+)-spirobrassinin.
Scheme 6: Opening of cyclic sulfamidates with thiol nucleophiles.
Scheme 7: Synthesis of androgen 20.
Scheme 8: Synthesis of (+)-BE-52440A.
Scheme 9: The Mitsunobu reaction.
Scheme 10: Mitsunobu substitution at a quaternary centre.
Figure 4: Initially assigned structure of hexacyclinol.
Scheme 11: Preparation of thioether 29.
Scheme 12: Thioethers 33 prepared from phosphinites 31.
Scheme 13: Preparation of enantiomerically pure thiol 39.
Scheme 14: Thioethers prepared by a modified Mitsunobu reaction.
Scheme 15: Nucleophilic conjugate addition.
Scheme 16: Asymmetric addition to cyclic enones.
Scheme 17: Preparation of thioether 45.
Scheme 18: Catalytic kinetic resolution of the enantiomers of enone 46.
Scheme 19: Organocatalytic conjugate addition to nitroalkenes 49.
Scheme 20: Preparation of β-amino acid 54.
Scheme 21: Sulfur migration within oxazolidine-2-thiones 56.
Scheme 22: Preparation of thiols 62 by self-regeneration of stereocentres.
Scheme 23: Synthesis of (5R)-thiolactomycin.
Scheme 24: Preparation of tertiary thiols and thioethers via α-thioorganolithiums.
Scheme 25: Diastereoselective methylation of organolithium 71.
Scheme 26: Addition to lithiated thiocarbamate 75.
Scheme 27: Configurational lability in unhindered α-lithiothiocarbamates.
Scheme 28: Configurational stability in bulky α-lithiothiocarbamates.
Scheme 29: Asymmetric functionalisation of secondary benzylic thiocarbamates.
Scheme 30: Methylation of lithioallyl thiocarbamates.
Scheme 31: Asymmetric preparation of tertiary allylic thiols.
Scheme 32: Asymmetric preparation of thiols 96 by aryl migration in lithiated thiocarbamates.
Oxidative cyclization of alkenols with Oxone using a miniflow reactor
- Yoichi M. A. Yamada,
- Kaoru Torii and
- Yasuhiro Uozumi
Beilstein J. Org. Chem. 2009, 5, No. 18, doi:10.3762/bjoc.5.18
- subsequent oxirane ring opening with the intramolecular oxygen nucleophile (an intramolecular SN2 reaction) to afford the product 2 stereospecifically [44][45]. It should be noted that the miniflow cyclization of 1a was continuously carried out to give a quantitative conversion of 2a over 2 h. Conclusion In
Graphical Abstract
Figure 1: Miniflow reaction system of oxidative cyclization.
Efficient 1,4-addition of α-substituted fluoro(phenylsulfonyl)methane derivatives to α,β-unsaturated compounds
- G. K. Surya Prakash,
- Xiaoming Zhao,
- Sujith Chacko,
- Fang Wang,
- Habiba Vaghoo and
- George A. Olah
Beilstein J. Org. Chem. 2008, 4, No. 17, doi:10.3762/bjoc.4.17
- of PMe3 to alkene 4 generates the dipolar intermediate. The latter abstracts a proton from the α-fluoro-substituted methylene derivative 3, followed by an intermolecular SN2 reaction to furnish the desired product 5 and the release of PMe3 (Scheme 1). The mechanism supports the fact that the less
Graphical Abstract
Scheme 1: Reaction mechanism for phosphine catalyzed 1,4-addition to α,β-unsaturated compounds.
