Chiral 2-Aminobenzimidazoles as Recoverable Organocatalysts for the Addition of 1,3-Dicarbonyl Compounds to Nitroalkenes<sup>†</sup>
作者:Diana Almaşi、Diego A. Alonso、Enrique Gómez-Bengoa、Carmen Nájera
DOI:10.1021/jo9010552
日期:2009.8.21
ole organocatalysts promote the conjugate addition of a wide variety of 1,3-dicarbonyl compounds such as malonates, ketoesters, and 1,3-diketones to nitroolefins in the presence of TFA as cocatalyst in toluene as solvent at rt or 0 °C. The Michael adducts are obtained in high yield and enantioselectivity, using the chiral 2-aminobenzimidazole 7b as hydrogen-bond-mediated chiral organocatalyst. This
手性反式-环己烷二胺-苯并咪唑有机催化剂在室温下以甲苯为溶剂,在TFA为助催化剂的情况下,促进多种1,3-二羰基化合物(如丙二酸酯,酮酸酯和1,3-二酮)与硝基烯烃的共轭加成反应。 0°C。使用手性2-氨基苯并咪唑7b可以高收率和对映选择性获得迈克尔加合物作为氢键介导的手性有机催化剂。可通过酸碱萃取后处理以94%的收率回收该催化剂。拟议的催化剂双功能布朗斯台德酸碱活化作用以及该过程的立体选择性的起源与DFT计算一致。根据这些计算,来自环己二胺键合的质子化叔胺激活了硝基烯烃,而苯并咪唑单元激活了1,3-二羰基亲核试剂。