Ruthenium-Catalyzed Synthesis of 2H-Azirines from Isoxazolinones.

2H-Azirines are synthetically versatile, highly strained, three-membered heterocycles containing an imino double bond. We report their efficient Ru-catalyzed synthesis using low catalyst loadings under neutral conditions from isoxazolinone substrates, which are readily accessible from β-ketoesters. The azirines were shown to be efficient precursors for functionalized pyridine, indole, dihydropyrrole, and pyrrolidine heterocycles.