Reaction of N-acyl and N-arylsulfonyl derivatives of 2-amino-3,3-dichloroacrylonitrile with phenylhydrazine

Cyclizations of N-acyl and N-alkoxycarbonyl derivatives of 2-amino-3,3-dich loroacrylonitrile with phenylhydrazine lead to formation of new functionall y substituted oxazoles and pyrazoles, respectively. By contrast, 2-arylsulf onylamino-3,3-dichloroacrylonitriles or, most probably, the corresponding a rylsulfonylimino tautomers with phenylhydrazine form only open-chain produc ts via replacement of the cyano group and two chlorine atoms by PhNHNH- and PhNHN= residues. Structurally related 2-[arylsulfonyl(methyl)amino]-3,3-di chloroacrylonitriles Cl2C=C(CN)N(CH3)SO2Ar, which are incapable of tautomer ic transformation, react with phenylhydrazine to give cyclocondensation pro ducts through participation of the two chlorine atoms and the cyano group; subsequent oxidation yields 5-amino-4-[arylsulfonyl(methyl)amino]-3-phenyla zopyrazoles. The structure of one of these products was proved by single cr ystal X-ray diffraction.