Azetinone formation is not competitive with intermolecular reactions of a β-lactam-4-ylidene
作者:Michel Zoghbi、John Warkentin
DOI:10.1139/v92-355
日期:1992.11.1
3-Phenoxy-1-phenyl-2-azetidinon-4-ylidene (β-lactam-4-ylidene) 2a, was generated by thermolysis of a spiro-fused β-lactam oxadiazoline precursor (1). Fast 1,2-H migration, a characteristic reaction of singlet carbenes that would convert 2a to 3-phenoxy-1-phenyl-3-azetin-2-one (4a) could not be demonstrated. Added 1, 3-diphenylisobenzofuran (6) did not afford the [4 + 2] cycloadduct (7) expected from
3-Phenoxy-1-phenyl-2-azetidinon-4-ylidene (β-lactam-4-ylidene) 2a 是通过热解螺-稠合 β-内酰胺恶二唑啉前体 (1) 产生的。无法证明快速 1,2-H 迁移,这是一种将 2a 转化为 3-phenoxy-1-phenyl-3-azetin-2-one (4a) 的单线态卡宾的特征反应。添加的 1, 3-二苯基异苯并呋喃 (6) 没有提供 4a 所预期的 [4 + 2] 环加合物 (7),而是提供异构的 E- 和 Z-4-[1-(2-苯甲酰基苯基)-1-苯基]-methylene-3-phenoxy-1-phenylazetidin-2-ones (9)。这些化合物可以被合理化为 6 和亚基的第一次形成的 [2 + 1] 加合物的重排产物。9的Z异构体的结构是通过单晶X射线衍射确定的。在甲醇-d4 中生成 2a,无论是纯的还是