rhodium(I)/H8-binap or binap complex catalyzes two different modes of cyclization of γ-alkynyl aldehydes with carboxylicacid anhydrides to give cyclic aldehyde gem-dicarboxylates and cyclic alkenyl esters through cleavage of the carboxylicacid anhydride C–O bond. The reaction of a terminal γ-alkynyl aldehyde with diethyl pyrocarbonate afforded a cyclic allylic carbonate with a high ee value.
Enantioselective Synthesis of Substituted δ-Lactones by Cooperative Oxidative N-Heterocyclic Carbene and Lewis Acid Catalysis
作者:Srikrishna Bera、Constantin G. Daniliuc、Armido Studer
DOI:10.1021/acs.orglett.5b01932
日期:2015.10.16
Efficient construction of complex cylcopentane- or cyclohexane-fused δ-lactones employing redox activation of enals using a chiral N-heterocycliccarbene and LiCl as cooperative catalysts is described. The organocascade proceeds with excellent diastereo- (>99:1) and enantioselectivity (up to >99% ee) and comprises the formation of three bonds with three contiguous stereocenters.
Catalytic Asymmetric Intramolecular α-Alkylation of Aldehydes
作者:Nicola Vignola、Benjamin List
DOI:10.1021/ja0392566
日期:2004.1.1
The development of a general catalyticasymmetricaldehyde alpha-alkylation reaction constitutes a major challenge in organic synthesis. Here, we report the first and successful approach toward its solution: (S)-alpha-methyl proline catalyzes the intramolecular alkylation of various halo aldehydes to the corresponding formyl cyclopentanes, -cyclopropanes, or -pyrrolidines in excellent yields and enantioselectivities