A Novel Heterocyclic Magenta Dye-Forming Coupler for Color Photographic Use: Synthesis of 1H-Pyrazolo(1,5-b)(1,2,4)triazole

1 H-Pyrazolo [1, 5-b] [1, 2, 4] triazole (1) is a novel 5, 5 fused ring system with a bridgehead nitrogen atom and a new type of magenta dye-forming coupler skeleton for color photographic use. The synthesis of 1 was achieved by two methods (A and B). In the method A, the 5, 5 fused ring was constructed by the reaction between an acid anhydride and a N-aminotriazolium compound (5) which was prepared by N-amination of 4-benzyl-3, 5-dimethyltriazole (4). The reaction of 5 with various acid anhydrides was studied to clarify the cyclization mechanism. In the method B, the 5, 5 fused ring was constructed by the dehydrating N-N bond formation of amidoximes (18) derived from 3-aminopyrazoles (16). This is the first example that the dehydrating procedure was adapted to N-N bond forming cyclization in the 5, 5 fused ring construction. The method B was applied to manufacturing magenta dye-forming couplers practically used in color photographs. This paper describes these synthetic methods in detail.