Protonation of Homoenolate Equivalents Generated by N-Heterocyclic Carbenes
作者:Karl Scheidt、Brooks Maki、Audrey Chan
DOI:10.1055/s-2008-1072516
日期:2008.4
Homoenolate equivalents are generated by Lewis basic N-heterocyclic carbene catalysts and then protonated to generate efficiently saturated esters from unsaturated aldehydes. This reactivity is extended to the generation of beta-acylvinyl anions from alkynyl aldehydes. The asymmetric protonation of a homoenolate equivalent generated from a beta,beta-disubstituted aldehyde can be accomplished with a
Conversion of α,β-Unsaturated Aldehydes into Saturated Esters: An Umpolung Reaction Catalyzed by Nucleophilic Carbenes
作者:Audrey Chan、Karl A. Scheidt
DOI:10.1021/ol050100f
日期:2005.3.1
species from alpha,beta-unsaturated aldehydes. These nucleophilic intermediates can be protonated, and the resulting activated carbonyl unit is trapped with an alcohol nucleophile, thereby promoting a highly efficient conversion of an alpha,beta-unsaturated aldehyde into a saturated ester. A kinetic resolution of secondary alcohols can be achieved using chiral imidazoylidene catalysts. [reaction: see text]
Ligand-Free Nickel-Catalysed 1,4-Addition of Arylboronic Acids to α,β-Unsaturated Carbonyl Compounds
作者:Wen Chen、Lu Sun、Xi Huang、Jiayi Wang、Yanqing Peng、Gonghua Song
DOI:10.1002/adsc.201400761
日期:2015.5.4
catalytic system has been developed for the 1,4‐addition of arylboronic acids to α,β‐unsaturatedcarbonylcompounds. With catalyst loadings of 1–2 mol%, a series of 1,4‐adducts from chalcones and cinnamates was obtained in moderate to excellent yields within 5–30 min under a nitrogen atmosphere and microwave irradiation. The 1,4‐addition of arylboronic acids to acrylates is less efficient.
unactivated amides is one of the most difficult challenges in organic chemistry, and an applicable method for cleaving amides used as directing groups in regioselective functionalization reactions has not been reported. Herein, we report direct catalytic alcoholysis of 8-aminoquinoline amides, which are highly effective directing groups in regioselective functionalization reactions. The reactions proceeded