Synthetic and mechanistic aspects of cross-coupling of nitroxyl radicals of 3-imidazoline series with terminal alkynes

Practical synthetic approaches to the new class of acetylenic derivatives of 3-imidazolyl-3-oxide-1-oxyls, including biradicals, were developed through cross-coupling reactions of 3-imidazolyl halides with either terminal alkynes or their copper salts. The presence of nitroxyl functional group as an internal oxidant leads to a competition between the formation of cross-coupling products and the products of oxidative homocoupling. The balance in this competition can be shifted toward the cross-coupling products through the combination of factors that includes nature of the catalyst, reactivity of the halides, and reaction conditions.