Vitamin B<sub>12</sub> Derivatives as Natural Asymmetric Catalysts: Enantioselective Cyclopropanation of Alkenes
作者:Ying Chen、X. Peter Zhang
DOI:10.1021/jo049870f
日期:2004.4.1
Vitamin B12 derivatives were found for the first time to be general and efficient catalysts for asymmetric cyclopropanation of alkenes with ethyl diazoacetate (EDA). Among several common derivatives, aquocobalamin (B12a) was shown to be the most effective catalyst for a variety of alkenes, providing cis-dominant cyclopropanes in excellent yields and moderate enantioselectivity. Reactivity studies under
首次发现维生素B 12衍生物是烯烃与重氮乙酸乙酯(EDA)不对称环丙烷化的通用且有效的催化剂。在几种常见的衍生物中,水合钴胺素(B 12a)被证明是多种烯烃最有效的催化剂,以优异的收率和中等的对映选择性提供了以顺位为主的环丙烷。在不同条件下的反应性研究表明,拟议的催化循环中的活性物质是基于钴的钴(II)阿拉明(B 12r),它可能是通过EDA原位还原B 12a产生的。