Electrophilic C(sp²)–H Cyanation with Inorganic Cyanate (OCN⁻) by Pᴵᴵᴵ/Pⱽ=O-Catalyzed Phase Transfer Activation

Abstract

A catalytic method for the direct electrophilic cyanation of C(sp²)–H nucleophiles with sodium cyanate (NaOCN) is reported. Mechanistic experiments show that under solid-liquid phase transfer, an inorganic cyanate is activated by halide displacement on a halophosphonium. Redox catalysis is enabled by the usage of a strained phosphine (phosphetane) so that catalyst turnover from phosphine oxide to phosphine can be easily achieved by the usage of a terminal hydrosilane reductant. These results demonstrate the feasibility of deoxyfunctionalization of insoluble inorganic salts by Pᴵᴵᴵ/Pⱽ=O catalyzed phase transfer activation, as exemplified by C(sp²)–H cyanation with NaOCN as the “CN⁺” source.