Borenium ion catalyzed hydroboration of alkenes with N-heterocyclic carbene-boranes.
Borenium ion catalyzed hydroboration of alkenes with N-heterocyclic carbene-boranes.
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DOI：
10.1021/ja305061c
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发表时间：
2012-07-25
影响因子：
15
通讯作者：
Vedejs E
中科院分区：
文献类型：
--
作者：
Prokofjevs A;Boussonnière A;Li L;Bonin H;Lacôte E;Curran DP;Vedejs E
用n -杂环碳衍生硼烷2和催化HNTf2在室温下处理3-己烯、3-辛烯和1-环己基-1-丁烯等烯烃。在3-己烯中，硼原子在几分钟到几小时的时间尺度内从己基的C3到C2的迁移速度惊人。氧化后处理的主要产物是含2-己醇的混合醇。在3-辛烯和1-环己基-1-丁烯氢化硼的氧化作用后，观察到对C(2)醇的类似偏好。nhc -硼离子（或功能等价物）被认为是完成硼氢化的物质，而C(2)选择性迁移归因于硼离子与nhc -硼烷烯烃阳离子π配合物的4中心相互转换。
Treatment of alkenes such as 3-hexene, 3-octene, and 1-cyclohexyl-1-butene with the N-heterocyclic carbene-derived borane 2 and catalytic HNTf2 effects hydroboration at room temperature. With 3-hexene, surprisingly facile migration of the boron atom from C3 of the hexyl group to C2 was observed over a time scale of minutes to hours. Oxidative workup gave a mixture of alcohols containing 2-hexanol as the major product. A similar preference for the C(2) alcohol was observed after oxidative workup of the 3-octene, and 1-cyclohexyl-1-butene hydroborations. NHC-borenium cations (or functional equivalents) are postulated as the species that accomplish the hydroborations, and the C(2) selective migrations are attributed to the 4-center inter-conversion of borenium cations with cationic NHC-borane olefin π-complexes.