Intermolecular and Intramolecular Cycloaddition Reactions of Azirines by Group 6 Metal Carbonyls and by Titanium Tetrachloride

Abstract

Reaction of 2-arylazirines with an equimolar amount of a group 6 metal carbonyl [M(CO)6, M = Cr, Mo, W] gives 2, 5-diarylpyrazines and isomeric dihydropyrazines in good combined yields. Isoxazoles, pyrazoles, and pyrroles can be synthesized in high yields, and under very mild conditions, by intramolecular cycloaddition of 3-phenyl-2-substituted-2H-azirines with molybdenum hexacarbonyl. These reactions occur via carbon-nitrogen bond cleavage of the azirine ring. Pyrazines, py-ridazines, α-chloro ketones, and monoketones were formed in low yield by titanium tetrachloride induced cleavage of the azirine ring. © 1977, American Chemical Society. All rights reserved.