Dinuclear Zinc Catalyzed Asymmetric Spirannulation Reaction: An Umpolung Strategy for Formation of α-Alkylated-α-Hydroxyoxindoles
作者:Barry M. Trost、Keiichi Hirano
DOI:10.1021/ol300577y
日期:2012.5.18
A highlydiastereo- and enantioselective formal [3 + 2] cycloaddition of α,β-unsaturated esters and 3-hydroxyoxindoles catalyzed by a dinuclear zinc-ProPhenol complex is reported. The stereoselective Michaeladditions of 3-hydroxyoxindoles and the subsequent transesterifications afford spirocyclic δ-lactones.
Dioxindole in Asymmetric Catalytic Synthesis: Routes to Enantioenriched 3-Substituted 3-Hydroxyoxindoles and the Preparation of Maremycin A
作者:Giulia Bergonzini、Paolo Melchiorre
DOI:10.1002/anie.201107443
日期:2012.1.23
nucleophilicity of dioxindole under different reaction conditions is key to a direct and easy access to valuable spiro oxindole γ butyrolactones and 3‐substituted 3‐hydroxyoxindole derivatives in excellent yields and enantioselectivities (see scheme). The preparation of maremycin A serves as an example for the potential usefulness of this previously unexplored reactivity in natural product synthesis.
activation of saturated acid chlorides by oxidative N-heterocycliccarbene catalysis has been successfully utilized to synthesize enantio-enriched spirooxindolelactones and δ-lactones. The reaction involves the transformation of the β sp3 carbon of saturated acid chlorides into an electrophilic carbon as a key step. The product was obtained in excellent yield and stereoselectivity.