New method for generation of β-oxido carbenoid via ligand exchange reaction of sulfoxides: A versatile procedure for one-carbon homologation of carbonyl compounds
one-carbon homologation of carbonylcompounds is described. The method is based on the rearrangement of β-oxido carbenoid which is generated via the ligand exchange reaction of the sulfinyl group of α-chloro β-hydroxy sulfoxide with tert-butyllithium. Addition of the carbanion of aryl 1-chloroalkyl sulfoxides to carbonylcompounds gave the adducts in good yields. The β-oxido carbenoid rearrangement of the
A novel method for generation of carbenoid from α-chloro sulfoxides: A new and versatile procedure for one-carbon homologation of carbonyl compounds to carbonyl compounds having an α-alkyl substituent
Addition of the carbanion of 1-chloroalkyl p-tolyl sulfoxides to carbonylcompound gave the adducts, which were treated with a base followed by t-butyllithium to afford one-carbon homologated carbonylcompounds having an alkyl group at the α-position, via the β-oxido carbenoids, in moderate to good yields.
Stereodivergent Synthesis of Trisubstituted Enamides: Direct Access to Both Pure Geometrical Isomers
作者:Luca Massaro、Jianping Yang、Suppachai Krajangsri、Emanuele Silvi、Thishana Singh、Pher G. Andersson
DOI:10.1021/acs.joc.9b01803
日期:2019.11.1
either (E)- or (Z)-isomers of trisubstituted enamides. Starting from an extensive range of ketones, it was possible to synthesize and isolate the desired pure isomer by switching the reaction conditions. Lewis acid activation enables the formation of the (E)-isomers in high stereoselectivity (>90:10) and good yields. On the other hand, the use of a Brønsted acid allows the preparation of the (Z)-isomers
作者:Eugenio Gandolfo、Xinjun Tang、Sudipta Raha Roy、Paolo Melchiorre
DOI:10.1002/anie.201910168
日期:2019.11.18
Photochemical enantioselective nickel-catalyzed cross-coupling reactions are difficult to implement. We report a visible-light-mediated strategy that successfully couples symmetrical anhydrides and 4-alkyl dihydropyridines (DHPs) to afford enantioenriched α-substituted ketones under mild conditions. The chemistry does not require exogenous photocatalysts. It is triggered by the direct excitation of
A highly efficient and selective rearrangement reaction of bromohydrins to aldehydes mediated by CF3CO2ZnEt was described. The secondary and tertiary aldehydes were prepared under mild conditions in good to excellent yields (85–99%). The scope and limitations of this rearrangement process were also investigated.
描述了由CF 3 CO 2 ZnEt介导的溴代醇对醛类的高效选择性重排反应。仲醛和叔醛是在温和的条件下以良好至极佳的收率(85–99%)制备的。还研究了这种重排过程的范围和局限性。