Synthesis and Reactions of a 2H-Azirine Unsubstituted on C–3

Thermolysis [¹] or photolysis [²] of 1-alkyl or 1-aryl-vinyl azides (1) (R¹ = R² = H, aryl, alkyl; R³= aryl, alkyl)[³] leads to the formation of 2H-azirines with a substituent at C-3 (2) and to ketenimines (3). However, the decomposition of “terminal” vinyl azides (1) (R¹ = R² == H, aryl, alkyl; R³ = H) gives only the nitriles (4) [⁴] and none of the expected, and formerly unknown, 2H-azirines which lack a substituent at the 3-position.