AbstractWe realized a highly efficient formal [1,2]‐sigmatropic rearrangement of ammonium ylides generated from 3‐methylene‐azetidines and α‐diazo pyrazoamides. The employ of readily available chiral cobalt(II) complex of chiral N,N′‐dioxide enabled the ring‐expansion of azetidines, affording a variety of quaternary prolineamide derivatives with excellent yield (up to 99 %) and enantioselectivity (up to 99 % ee) under mild reaction condition. For the rearrangement of ammonium ylides, the installation of a pyrazoamide group as a masked brick to build chiral scaffolds proved successful. The enantioselective ring expansion process was elucidated by DFT calculations.
摘要 我们实现了由 3-亚甲基氮杂环丁烷和α-重氮吡唑酰胺生成的铵酰化物的高效形式[1,2]-对位重排。利用易于获得的手性 N,N′-二氧化物的手性钴(II)配合物实现了氮杂环丁烷的扩环,在温和的反应条件下获得了多种季脯氨酸酰胺衍生物,具有极佳的收率(高达 99 %)和对映选择性(高达 99 % ee)。事实证明,在酰化铵的重排过程中,安装一个吡唑酰胺基团作为掩蔽砖来构建手性支架是成功的。DFT 计算阐明了对映体选择性扩环过程。