Electron-Transfer Driven Cyanation of Aryl Iodides

Abstract

Aryl cyanides are widely utilized as important intermediates in the research fields of pharmaceuticals, natural products and also organic materials, because the nitrile group can easily be transformed into a wide variety of functional groups, such as amides, carboxylic acids, imines, ketones, and amines. In the preparation of aryl cyanides, Rosenmund–von Braun reaction, in which an aryl halide reacts with copper cyanide, is often used; however, harsh reaction conditions are required, and the separation of cupper complexes in a workup process is often problematic, especially in a large-scale synthesis. We initiated our study to develop a copper free method to prepare aryl cyanides, and found that a catalytic amount of 1,10-phenanthroline nicely promoted the reaction of aryl iodides with tetraethylammonium cyanide to afford aryl cyanides (Scheme 1). 1,10-phenanthroline would work as a SET initiator on the first stage to generate radical anion. We next tried to use the electrochemical reaction for the initiation step. Electricity was simply passed to the mixed solution of aryl iodides and tetraethylammonium cyanide to afford the corresponding aryl cyanides in moderate yields. Notably, the reactions proceeded with a catalytic amount of electricity. Figure 1