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

An organophosphorus redox‐catalyzed method for the direct electrophilic cyanation of C(sp2)–H nucleophiles with sodium cyanate (NaOCN) is reported. The catalytic deoxyfunctionalization of the OCN– anion is enabled by the use of a small‐ring phosphacyclic (phosphetane) catalyst in combination with a terminal hydrosilane O‐atom acceptor and a malonate‐derived bromenium donor. In situ spectroscopy under single‐turnover conditions demonstrate that insoluble inorganic cyanate anion is activated by bromide displacement on a bromophosphonium catalytic intermediate to give a reactive N‐bound isocyanatophosphonium ion, which delivers electrophilic “CN+” equivalents to nucleophilic (hetero)arenes and alkenes with loss of a phosphine oxide. These results demonstrate the feasibility of deoxyfunctionalization of insoluble inorganic salts by PIII/PV=O catalyzed phase transfer activation.