Tandem radical cyclization of acyclic homoallylic xanthates: cyclopentannulated .gamma.-thionolactone and .gamma.-lactones
摘要:
The first tandem radical cyclization of linear homoallylic xanthates was explored. Homoallylic xanthates prepared from alpha,beta-unsaturated esters were easily cyclized by tin hydride with an radical initiator to give the corresponding thionolactone annulated cyclopentane skeleton in a high yield. The stereochemistry of cyclized products was also discussed. Thionolactones obtained were oxidized chemoselectivity with m-CPBA under neutral condition to afford gamma-lactones in a high yield.
Facile synthesis of α, β-unsaturated esters through a one-pot copper-catalyzed aerobic oxidation-Wittig reaction
作者:Cheng Ren、Zhenyu Shi、Weijie Ding、Zhiqing Liu、Huile Jin、Xiaochun Yu、Shun Wang
DOI:10.1016/j.tetlet.2017.09.020
日期:2018.1
An efficient one-pot synthesis of α, β-unsaturated estersthrough the aerobic oxidation – Wittig tandem reaction of alcohols and phosphorous ylide is developed. This new method operates under mild reaction conditions, and uses CuI/TEMPO (TEMPO = 2,2,6,6-tetramethylpiperidine-N-oxyl) as co-catalyst and air (O2) as the oxidant. It tolerates a wide range of functionalized benzylic alcohol and aliphatic
Diastereoselective [2,3]-sigmatropic rearrangements of lithium N-benzyl-O-allylhydroxylamides bearing a stereogenic centre adjacent to the migration terminus
作者:Steven D. Bull、Stephen G. Davies、Sara Hernández Domíngez、Simon Jones、Anne J. Price、Thomas G. R. Sellers、Andrew D. Smith
DOI:10.1039/b207069n
日期:——
3]-sigmatropic rearrangements of lithium N-benzyl-O-allylhydroxylamides bearing a stereogenic centre adjacent to the migrationterminus are examined. (E)-N-Benzyl-O-(4-phenylpent-2-enyl)hydroxylamine rearranges in 30% de to afford syn-(3RS,4RS)-3-(N-benzyl-N-hydroxy)-4-phenylpent-1-ene as the major diastereoisomer, consistent with the rearrangement proceeding under moderate steric control. Rearrangements of both
Highly (<i>E</i>)-Selective Wadsworth−Emmons Reactions Promoted by Methylmagnesium Bromide
作者:Timothy D. W. Claridge、Stephen G. Davies、James A. Lee、Rebecca L. Nicholson、Paul M. Roberts、Angela J. Russell、Andrew D. Smith、Steven M. Toms
DOI:10.1021/ol802212e
日期:2008.12.4
An experimentally simple protocol for the very highly (E)-selective Wadsworth-Emmonsreaction [(E):(Z) selectivities in excess of 180:1 in some cases] of a range of straight-chain and branched aliphatic, substituted aromatic, and base-sensitive aldehydes via reaction with an alkyl diethylphosphonoacetate and MeMgBr is reported.
Copper-Catalyzed Decarboxylative Trifluoromethylation of Allylic Bromodifluoroacetates
作者:Brett R. Ambler、Ryan A. Altman
DOI:10.1021/ol402780k
日期:2013.11
this transformation typically requires four-step processes, specialty chemicals, and/or stoichiometric metals to access the trifluoromethyl-containing product. A two-step copper-catalyzed decarboxylative protocol for converting allylic alcohols to trifluoromethanes is reported. Preliminary mechanistic studies distinguish this reaction from previously reported Cu-mediated reactions.
Diastereoselectivity of the thio-Claisen rearrangement of acyclic precursors bearing a chiral centre adjacent to carbon 6
作者:Stéphane Désert、Patrick Metzner
DOI:10.1016/s0040-4020(01)88337-x
日期:1992.11
allylic alcohols have been prepared and submitted to a Mitsunobu reaction with dithioacetic acid. Allyl dithioesters were deprotonated by LDA at −30°C and resulting enethiolates were quenched with iodomethane to afford quantitatively S-allyl ketenedithioacetals. These precursors undergo a thio-Claisenrearrangement under smooth conditions: room temperature or heating at 101°C. The diastereoselectivity of