2,3,5-Trichloro-4,4-ethylenedioxy-2-cyclopentenone reacted with sodium azide in tetrahydrofuran to give the expected 3-azido derivative which was converted into 1,3-dichloro-4,4-ethylenedioxy-6-azabicyclo-[3.1.0]hex-5-en-2-one and 3-amino-2,5-dichloro-4,4-ethylenedioxy-2-cyclopentenone on heating in chloroform. The reaction of 2,3,5-trichloro-4,4-ethylenedioxy-2-cyclopentenone with potassium thiocyanate, depending on the conditions, afforded the corresponding 3-thiocyanato derivative or symmetric sulfide. Treatment of the title compound with hydroxylamine resulted in opening of the dioxolane ring with simultaneous formation of oxime via replacement of chlorine at the neighboring sp 2 -carbon atom. a: NaN 3 , THF, 20°C (82% from I; 71% from II); b: PhSNa, THF-MeOH (85%); c: m-ClC 6 H 4 CO 3 H, CH 2 Cl 2 (79%); d: CHCl 3 , ∆, (V, 70%; VI, 10%); e: Zn-THF-NH 4 Cl, ∆ (20%); f: 20% hydrochloric acid, Me 2 CO (60%).In the past decade, the synthesis and transformations of azirines have attracted persistent attention [1][2][3][4][5][6][7][8][9][10]. This interest originates from both specific chemical properties of highly strained cyclic imines and isolation of a series of natural antibiotics having an azirine structure (e.g., azirinomycin [11], enantiomeric dizidazirines [12], and antazirine [13]). The most practical and general procedures for the synthesis of azirines are based on thermal and photochemical decomposition of vinyl azides, which involve interScheme 1.