Organocatalytic Asymmetric Alkylation of Aldehydes by SN1-Type Reaction of Alcohols
作者:Pier Giorgio Cozzi、Fides Benfatti、Luca Zoli
DOI:10.1002/anie.200805423
日期:2009.2.2
Work‐alcoholic! The elusive enantioselective catalytic α‐alkylation of aldehydes, a widely sought transformation, was brought to execution by the use of alcohols capable of forming stabilized carbocations (see scheme, TFA=trifluoroacetic acid).
Enantioselective Organocatalytic α-Alkylation of Ketones by SN1-Type Reaction of Alcohols
作者:Maria Trifonidou、Christoforos G. Kokotos
DOI:10.1002/ejoc.201101509
日期:2012.3
The enantioselective α-alkylation reaction of cyclic ketones is described. Our catalyst, based on a “privileged” pyrrolidine ring bearing a chiral thioxotetrahydropyrimidinone ring, is a highly reactive catalyst for cyclic ketones. When this catalyst was coupled with in situ generated carbocations derived from alcohols, the corresponding α-alkylated adducts were obtained in moderate to quantitative
Cooperative Organocatalysis for the Asymmetric γ Alkylation of α-Branched Enals
作者:Giulia Bergonzini、Silvia Vera、Paolo Melchiorre
DOI:10.1002/anie.201004761
日期:2010.12.10
α Branched leads to γ: The direct and enantioselective γalkylation of α‐substituted α,β‐unsaturated aldehydes under dienamine catalysis has been achieved. A cooperative catalysis system that involves dienamine activation of α‐branched enals and chiral Brønsted acid catalysis promotes an SN1‐alkylation pathway while ensuring complete γ‐site selectivity and high stereocontrol (see scheme; Bn=benzyl)
α分支导致γ:在二烯胺催化下,实现了α-取代的α,β-不饱和醛的直接和对映选择性γ烷基化。一个合作的催化系统涉及α-支链烯类的二烯胺活化和手性布朗斯台德酸催化,可促进S N 1烷基化途径,同时确保完全的γ位选择性和高度立体控制(参见方案; Bn =苄基)。
Enantioselective Tandem Reactions at Elevated Temperatures: One-Pot Hydroformylation/SN1 Alkylation
作者:Julian Stiller、Andreas J. Vorholt、Karoline A. Ostrowski、Arno Behr、Mathias Christmann
DOI:10.1002/chem.201200639
日期:2012.7.27
Canned heat: The optimization of a tandem sequence of a metal‐catalyzed and a subsequent organocatalytic reaction is described (see figure). The tandem sequence was initially optimized toward a high yield by variations of substrate ratio, rhodium precursor, and ligands. The tandemreaction is also extendable to more complex alkenes and to substrates with additional functional groups.
The versatile roles of ammonium salt catalysts in enantioselective reduction and alkylation of α,β-unsaturated aldehydes: iminium catalysis, enamine catalysis and acid catalysis
A novel strategy for highly efficient utilization of chiral ammonium salt catalysts has been described in this paper. Three kinds of catalytic functions including iminium catalysis, enaminecatalysis, and acid catalysis of chiral ammonium salt catalysts, have been achieved in the enantioselective reduction and alkylation reaction of alpha,beta-unsaturated aldehydes with alcohols.