Stereoselective Reactions of Phthalimido-Substituted Radicals Derived from (±)-Threonine: A comparison with reactions of<i>N</i>-phthaloyliminium ions
作者:Aleksandar Stojanovic、Philippe Renaud、Kurt Schenk
DOI:10.1002/hlca.19980810208
日期:1998.2.4
Stereoselective reactions of phthalimido-substituted radicals derived from (±)-threonine with different radical traps are reported (Scheme 3, Table 1). A strong influence of the nature of the radical trap on the stereoselectivity was noticed. Small nucleophilic radical traps gave preferentially the syn products. The observed selectivities are explained with the A1,3 strain model and depend on steric
报道了衍生自(±)-苏氨酸的邻苯二甲酰亚胺基取代的自由基与不同的自由基陷阱的立体选择反应(方案3,表1)。注意到自由基陷阱的性质对立体选择性的强烈影响。小的亲核自由基陷阱优先提供了syn产物。观察到的选择性用A 1,3应变模型解释,并取决于空间效应和电子效应(图2)。与电自由基捕获剂如二苯基二硒化物的反应给了反映异构体中度立体控制,这可能是由于立体电子效应。相同的立体化学结果,即观察到相关产物N-邻苯二甲酰亚胺鎓离子的反应优先形成抗产物(方案5,表2)。离子反应的立体化学通过Felkin-Anh模型得以合理化(图3)。