Organocatalytic conjugate addition of 1-bromonitroalkanes to α,β-unsaturated aldehydes: synthesis of nitrocyclopropanes
作者:Jun-min Zhang、Zhi-peng Hu、Shuang-qi Zhao、Ming Yan
DOI:10.1016/j.tet.2008.11.060
日期:2009.1
A variety of secondary amines were studied as the catalyst in the conjugate addition of 1-bromonitromethane to alpha,beta-unsaturated aldehydes. Proline was identified as the best catalyst for this reaction. MeOH/AcONa system was found to provide much better yields than CHCl3/Et3N system reported before. Good yields of nitrocyclopropane products were obtained with a variety of beta-aryl acroleins. Several substituted 1-bromonitrornethanes were also examined in the reaction. Both 1-bromonitroethane and 1-phenyl-1-bromonitromethane gave the corresponding nitrocyclopropanes in good yields. The diastereo-selectivity of the reaction was strongly affected by the steric hindrance of 1-bromonitroalkanes. (C) 2008 Elsevier Ltd. All rights reserved.