Another Way To Functionalize Alkynes

Alkynes are versatile reagents that lend themselves to an array of functionalizations—oxidation, cross-coupling, cyclo­addition, and metathesis reactions, to name a few. In seeking out additional examples, Uttam Dutta and Debabrata Maiti of Indian Institute of Technology Bombay (IITB) and David W. Lupton of Monash University have teamed up to develop the first example of metal-free nitrogenation of terminal alkynes to produce aryl nitriles (Org. Lett. 2016, DOI: 10.1021/acs.orglett.6b00147). The team, part of the IITB-Monash Research Academy, developed the reaction based on the Maiti group’s earlier successes in using tert-butyl nitrite for the C–H functionalization of alkenes and alkynes to make nitroolefins and α-nitroketones, respectively. When the researchers came across literature reports of using trimethylsilylazide as a reagent for converting alkynes to nitriles, it occurred to them that tert-butyl nitrite could provide a safer and cost-effective alternative to azides. The Maiti-Lupton team coupled tert-butyl nitrite with 2-picoline-N-oxide as an oxidant to make more than three dozen aryl and heteroaryl nitriles up to gram scale (one shown), including natural product derivatives such as converting the alkynyl ester of vitamin E to a nitrile.