Cyanation of Alcohols with Diethyl Cyanophosphonate and 2,6-Dimethyl-1,4-benzoquinone by a New Type of Oxidation–Reduction Condensation

Cyanation of various alcohols by a new type of oxidation–reduction condensation is described. Primary alkyl diphenylphosphinites, 2,6-dimethyl-1,4-benzoquinone (DMBQ), and diethyl cyanophosphonate gave the corresponding nitriles in high yields. During the above experiment on cyanation of 4-phenylbutan-2-ol, the unexpected formation of a mixture of nitrile and isocyanide was observed. After careful examination of the reaction conditions, selective synthesis of isocyanides from secondary alcohols was successfully accomplished by the use of zinc oxide (ZnO) as an additive. Reaction of tertiary alcohols provided the corresponding isocyanides exclusively in the absence of an additive. Cyanation of optically active alcohols was tried in order to clarify the stereochemistry of this reaction, and the reaction was thus proved to proceed with the inversion of configuration.