Alkyne and reversible nitrile activation: N,N'-diamidocarbene-facilitated synthesis of cyclopropenes, cyclopropenones, and azirines.

We report the synthesis of a variety of diamidocyclopropenes by combining an isolable and readily accessible N,N'-diamidocarbene (DAC) with a range of alkynes (nine examples, 68-97% yield). Subsequent hydrolysis of selected cyclopropenes afforded the corresponding cyclopropenones or α,β-unsaturated acids, depending on the reaction conditions. In addition, the combination of a DAC with alkyl or aryl nitriles was found to form 2H-azirines in a reversible manner (four examples, K(eq) = 4-72 M(-1) at 30 °C in toluene).