A facile N-heterocyclic carbene catalytic enantioselective aza-Diels–Alder reaction of oxodiazenes with α-chloroaldehydes as dienophile precursors is reported, with excellent enantioselectivity (ee > 99%) and excellent yield (up to 93%). DFT study showed that cis-TSa, formed from a top face approach of oxodiazene to cis-IIa, is the most favorable transition state and is consistent with the experimental
Diasteroselective Preparation of Cyclopropanols Using Methylene Bis(iodozinc)
作者:Kevin Cheng、Patrick J. Carroll、Patrick J. Walsh
DOI:10.1021/ol200597h
日期:2011.5.6
A diastereoselective synthesis of trans-2-substituted cyclopropanols is outlined. Bimetallic CH2(ZnI)(2) was found to react with alpha-chloroaldehydes to give cyclopropanols in yields of 64-89% and dr's >= 10:1. The high trans-selectivity resulted from equilibration of the cyclopropoxide intermediates.
<i>N</i>-Heterocyclic Carbene (NHC)-Catalyzed Highly Diastereo- and Enantioselective Oxo-Diels–Alder Reactions for Synthesis of Fused Pyrano[2,3-<i>b</i>]indoles
作者:Limin Yang、Fei Wang、Pei Juan Chua、Yunbo Lv、Liang-Jun Zhong、Guofu Zhong
DOI:10.1021/ol301175z
日期:2012.6.1
A chiral N-heterocyclic carbene (NHC)-catalyzed Diels-Alder reaction of 2-oxoindolin-3-ylidenes and alpha-chloroaldehydes was developed for the synthesis of fused pyrano[2,3-b]indoles in good to excellent yields (up to 99%) with high cis-diastereoselectivities (>99:1 dr) and enantioselectivities (up to >99% ee).