Ethyl o-azidobenzimidate (6) and o-azidobenzamidine (7) on thermolysis yield 3-ethoxy-(9 ; X = OEt) and 3-amino-IH-indazole (9; X = NHJ, respectively. The former product is also obtained on irradiation of the imidate in methanol-tetrahydrofuran solution.2-Aryl-and 2heteroaryl-3-chloro-2H-indazoles have been prepared by the action of hot thionyl chloride on o-azidoanilides. The trichloro-2H-indazoles obtained by the action of phosphorus pentachloride on o-azidobenzanilide (1 2) and by the action of thionyl chloride on N-(0-azidobenzoyl) -2aminopyridine have been identified as the 3,5,7-trichloro derivatives. The reductive dehalogenation, nitration, and reactivity of the halogen towards nucleophiles, of 3-chloro-2-phenyl-2H-indazole (1 9) are reported.A new practicable synthesis of o-azidobenzaldehyde (31 ; X = 0) is described. Thermolysis of its phenyl hydrazone and semicarbazone derivatives yields 2H-indazoles.

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