Asymmetric induction in Darzens condensation by means of (−)-8-phenylmenthyl and (−)-menthyl auxiliaries
作者:Ryukichi Takagi、Jyunji Kimura、Yoshihiro Shinohara、Yuko Ohba、Kyoko Takezono、Yoshikazu Hiraga、Satoshi Kojima、Katsuo Ohkata
DOI:10.1039/a707310k
日期:——
Asymmetric Darzens condensation of benzaldehyde and various ketones has been investigated. The condensation of acetophenone, propiophenone and symmetric ketones with (–)-8-phenylmenthyl halogenoacetates 3a,b afforded the corresponding glycidic esters cis-12, cis-13 and 15–19 in 77–96% de, respectively, as the major products. Aza-Darzens condensation between N-benzylideneaniline and 3a occurred to give
已经研究了苯甲醛和各种酮的不对称Darzens缩合。苯乙酮,丙苯酮和对称酮与(–)-8-苯基薄荷基卤代乙酸酯3a,b的缩合分别提供77-96%de的相应缩水甘油酯顺式-12,顺式-13和15-19,这是主要产物。在N-亚苄基苯胺和3a之间发生Aza-Darzens缩合,得到反式-氮丙啶21作为主要异构体,其de> 85%。顺式-12和18的主要非对映异构体的立体化学通过将其转化为已知的旋光性二醇22和24得以证实。顺式-12的主要产物的构型确定为2[R,3 - [R和18的是2 - [R。几何形状和地表选择性在初始醛醇型反应中可以理解为开链或非螯合的反平面的非平面过渡态模型。