Abstract

   Electrochemical transformations of epoxides have emerged as a useful and sustainable platform for alcohol synthesis, and their reactivity and selectivity strongly dictated by the substitutions of the epoxides. Incorporation of an alkynyl substituent into the epoxide framework offers a promising yet unexplored avenue toward highly functionalized different alcohol derivatives posing formidable challenges in selectivity control.  Here we report an earth-abundant metal of nickel-catalyzed cross-electrophile coupling between readily available alkynyl epoxides and aryl halides, enabling the highly selective synthesis of allenols under mild electrochemical conditions. This protocol exhibits a broad substrate scope, preferential C–O bond activation over C–X bonds, and a decent chemoselectivity for C–I activation over C-Br bond, while tolerating a wide array of synthetically valuable functional groups, such as free hydroxyl, ketone, carboxylate, methoxy, TBS ether, N-Boc, highly strained cyclopropyl, C=C bond, C–TMS, C–F bond, C–Cl bond, C–Br bond, and even C–B bond. Moreover, this methodology may also apply to the synthesis of allenols bearing pharmaceutical and biologically active moieties and the downstream derivatizations of allenol products have also been realized, offering a modular platform for the synthesis of diversified functional structures.

Wenyao Li (李文耀)