chloride and alkyl 2-diazo-3-(3-substituted-2-oxopiperidin-3-yl)-3-oxopropanoates were treated with rhodium(II) acetate. Attack of the imido carbonyl oxygen at the resultant rhodium carbenoid center produced a transient push-pull carbonyl ylide dipole which underwent an intramolecular dipolar cycloaddition across the indole π-bond. In most cases, the resulting cycloadduct is the consequence of ENDO-cycloaddition
一系列由 (1 H-indol-3-yl)
乙酰氯和烷基 2-重氮-3-(3-取代-2-氧代
哌啶-3-基)-
3-氧代丙酸酯制备的重
氮酮酰亚胺用
铑(II)处理)
醋酸盐。亚
氨基羰基氧在所得
铑卡宾中心的攻击产生了瞬态推拉羰基叶立德偶极子,该偶极子在
吲哚π-键上经历了分子内偶极环加成。在大多数情况下,产生的环加合物是关于偶极子的 ENDO 环加成的结果,这完全符合最低能量过渡态。有趣的是,当
乙酸叔丁酯取代基位于起始重
氮酮亚胺的环连接处时,EXO-环加合物是获得的唯一产物。在这种情况下,