Development of an Operationally Simple, Scalable, and HCN-Free Transfer Hydrocyanation Protocol Using an Air-Stable Nickel Precatalyst

Abstract

Hydrocyanation reactions enable access to synthetically valuable nitriles from readily available alkene precursors. However, hydrocyanation reactions using hydrogen cyanide (HCN) or similarly toxic reagents on laboratory scale can be particularly challenging due to their hazardous nature. In addition, such processes typically require air- and temperature-sensitive Ni(0) precatalysts, further reducing the operational simplicity of this transformation. Herein, we report a HCN-free transfer hydrocyanation of alkenes and alkynes that employs commercially available aliphatic nitriles as sacrificial HCN donors in combination with a catalytic amount of air-stable and inexpensive NiCl2 as a precatalyst and a cocatalytic Lewis acid. The scalability and robustness of the catalytic process were demonstrated by the hydrocyanation of α-methylstyrene on a 100 mmol scale (11.4 g of product obtained) using 1 mol % of the Ni catalyst. In addition, the feasibility of the dehydrocyanation protocol using the air-stable Ni(II) precatalyst and norbornadiene as a sacrificial acceptor was showcased by the selective conversion of an aliphatic nitrile into the corresponding alkene.