showed that all Schiff bases studied favor the enol-imine form over the keto form in a weakly polar solvent such as deuterochloroform.

3-Oxo-2-arylhydrazononitriles 1a-c react readily with chloroacetonitrile, ethyl chloroacetate, and with phenacyl chloride to give 4-aminopyrazoles 4a-e. The pyrazolo [4,3-d]pyrimidine derivatives 7 and 10 are synthesized via reaction of the aminopyrazole 4b with phenylisothiocyanate and DMFDMA/NH 4 OAc respectively.

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The six-membered N-heterocyclic ring of the title compound, C17H15ClN2O, is fused with a methyl-substituted cyclo­hexene ring. The approximately planar nitro­gen-bearing ring (r.m.s. deviation 0.019 Å) is aromatic, and the N atom shows a trigonal–planar coordination; its benzene substituent is aligned at 77.1 (1) °. The cyclo­hexene ring adopts a half-chair conformation. In the crystal, inversion-related mol­ecules are linked by pairs of N—H⋯O hydrogen bonds, generating dimers.

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