We have developed a protocol for insertion of alkylidene carbenes into the B-H bonds of amine-borane adducts, enabling, for the first time, the construction of C(sp2)-B bonds by means of carbene-insertion reactions. Various acyclic and cyclic alkenyl borane-amine adducts were prepared from readily accessible starting materials in good to high yields and were subsequently subjected to a diverse array of functional group transformations. The unprecedented spiro B-N heterocycles prepared in this study have potential utility as building blocks for the synthesis of pharmaceuticals. Preliminary mechanistic studies suggest that insertion of the alkylidene carbenes into the B-H bonds of the amine-borane adducts proceeds via a concerted process involving a three-membered-ring transition state.

中文翻译：

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亚烷基卡宾插入 B-H 键

我们开发了一种将亚烷基卡宾插入胺-硼烷加合物的 BH 键的协议，从而首次通过卡宾插入反应构建 C(sp2)-B 键。各种无环和环状链烯基硼烷-胺加合物由容易获得的起始材料以良好到高产率制备，然后进行各种官能团转化。本研究中制备的史无前例的螺 BN 杂环作为药物合成的基础材料具有潜在的实用性。初步机理研究表明，亚烷基卡宾插入胺-硼烷加合物的 BH 键是通过涉及三元环过渡态的协同过程进行的。