The Cu(II)-catalyzed addition of two molecules of a 3-aryl-2H-azirine to diazotetramic or diazotetronic acids proceeds as a domino reaction with the formation of 1,2,3-triazole derivatives with ortho-fused (pyrrolo[3,4-b]pyrrol or furo[3,4-b]pyrrol) and spiro-cyclic (1-oxa-4,7-diazaspiro[4.4]nonane or 1,7-dioxa- 4-azaspiro[4.4]nonane) substituents at the N2 position. The disclosed reaction is a new type of formation of a 1,2,3-triazole ring from (N–N) and (C–C–N) building blocks.