Alkyne and Reversible Nitrile Activation: <i>N</i>,<i>N</i>′-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, Keq = 4–72 M–1 at 30 °C in toluene).