The use of two optically active N-sulfinyl α-imino esters in the stereoselective aza-Diels–Alder reaction
作者:Trygve Andreassen、Marianne Lorentzen、Lars-Kristian Hansen、Odd R. Gautun
DOI:10.1016/j.tet.2009.01.090
日期:2009.4
Diastereoselective aza-Diels–Alder (aza-DA) reactions of ethyl (S)-N-(tert-butanesulfinyl)iminoacetate (2a) and ethyl (S)-N-(p-toluenesulfinyl)iminoacetate (2b) with different dienes including activated, non-activated, cyclic, and acyclic dienes in the presence of Lewis acids are described. Reactions with 2a were found to be more selective. Reactions of unactivated dienes (acyclic and cyclic) with
非对映选择性氮杂狄尔斯-阿尔德(氮杂-DA)乙基的反应(小号) - ñ - (叔-butanesulfinyl)iminoacetate(图2a)和乙基(小号) - ñ - (p -toluenesulfinyl)iminoacetate(2B)具有不同的二烯包括描述了在路易斯酸存在下的活化,非活化,环状和无环二烯。发现与2a的反应更具选择性。未活化的二烯(无环和环状)与化学计量的TMSOTf作为路易斯酸的反应以适中的收率和高达99%的非对映选择性提供了aza-DA加合物。观察到强烈倾向于重新接近2a。环二烯使exo加合物成为主要产物。对于与活化的Danishefsky型二烯的氮杂-DA反应,观察到较差的非对映选择性。在这些情况下,使用化学计量的BF 3 ·Et 2 O作为路易斯酸可获得最佳结果(最高69%de,76%收率)。通过与已知化合物的化学相关性确定了六种加成产物的绝对构型。在没有