Enantioselective cyclopropane syntheses using the chiral carbene complexes (SFe)- and (RFe)-C5H5(CO)(PR3)Fe:CHCH3+. A mechanistic analysis of the carbene transfer reaction
作者:Maurice Brookhart、Yumin Liu、Emma W. Goldman、Debra A. Timmers、Gregory D. Williams
DOI:10.1021/ja00003a028
日期:1991.1
ethylidene transfer from these complexes to styrene, vinylacetate, and isopropenyl acetate gave methylcyclopropanes in high optical yields. A mechanistic analysis of the transferreaction is presented by using the stereochemical results obtained coupled with deuterium labeling and relative reactivity studies. It is concluded that the most likely mechanism for carbene transferinvolvesreaction of the
通过使用标准技术将对映体纯的酰基配合物转化为相应的对映体纯的卡宾配合物(S Fe )-和(R Fe )-C 5 H 5 (CO)(PR 3 )Fe=CHCH 3 + 。对映选择性亚乙基从这些配合物转移到苯乙烯、乙酸乙烯酯和乙酸异丙烯酯,得到高光学产率的甲基环丙烷。通过使用获得的立体化学结果以及氘标记和相对反应性研究,对转移反应进行了机理分析。得出的结论是,卡宾转移的最可能机制涉及烯烃与 C 5 H 5 (CO)(PR 3 )Fe=CHCH 3 + 的次要但更具反应性的向斜异构体的反应,然后是发展中的亲电子中心的背面攻击在 Fe-Cα 键上的 Cγ。