Reactions with Cyclic Amidenes III: Synthesis of Some New Fused Pyrazole Derivatives

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Abstract
Diazotised 5-amino-3-hydroxy-4-phenylazopyrazole (1 a) and 3,5-diamino-4-phenylazo-pyrazole(1 b) coupled with active methylene reagents to yield the pyrazolo[1,5-c]-as-triazine derivatives (3a, b-5 a, b). On the other hand coupling of diazotised 1 a, with β-naphthal has afforded the acyclic azo derivative(6). Whereas diazotised 1 a underwent intramolecular cyclisation into the pyrazolo[1,5-c]-1,2,3,4-tetrazine derivative (3)on attemptet addition to acrylonitrile, diazotised 1 b reacted with acrylonitrile under the same conditions to yield the pyrazolo[1,5-c]-pyridazine derivative (4). Compounds 1 a, b reacted with benzoylisothiocyanate to yield the pyrazol-5-ylthiourea derivatives (10 a, b). Where as 10 a readily cyclised into the pyrazolo[3,4-c]-as-triazine derivative (11) on refluxing with pyridine, compound 10 b hydrolysed under the same conditions into the pyrazol-5-ylthiourea derivative (12).