comparable. Additions catalyzed by 1 are strongly sensitive to steric effects. Highly substituted olefins afford cyclopropanes in only poor yield. The preferential cis-selectivity observed in reactions catalyzed by 1 is attributed to dominant interactions between the ligand of the catalyst and the substituents of both olefin and diazoacetate, which overrule the steric interactions between olefin and diazoacetate
用[Rh 2 (4 S)-phox} 4 ](1 ; phox =四[[4 S)-四氢-
4-苯基恶唑-2-酮])研究了Rh 11催化的
重氮乙酸类
酯类化合物向烯烃的加成反应。,[Rh 2 ((2 S)-mepy} 4 ](2 ; mepy =四[甲基(2 S)-四氢-5-氧杂
吡咯-2-羧酸酯])和[Rh 2(OAc)4 ](3)。当用2和3催化时,优先提供反式-
环丙烷羧酸酯,顺式-异构体是1的主要产品。通常,用1和2获得的对映选择性是可比较的。1催化的加成对位阻效应非常敏感。高度取代的烯烃仅以较差的收率提供
环丙烷。在1催化的反应中观察到的优先顺式选择性归因于催化剂的
配体与烯烃和
重氮乙酸酯的取代基之间的显性相互作用,该相互作用抵消了烯烃和
重氮乙酸酯在过渡态下的卡宾转移的空间相互作用。