Synthesis of substituted indenopyrazoles

Tricyclic systems having the indenopyrazole nucleus were synthesized as potential CNS agents. The starting materials, 3-substituted indeno[1,2-c]pyrazol-4(1H)-ones, were prepared as reported in the literature. 3-Methylindeno[1,2-c]pyrazol-4(1H)-one (XXIV) was synthesized by the cyclization of the monohydrazone of 2-acetyl-1, 3-indandione using phosphorous pentoxide in benzene. Alkylation of sodium 3-methylindeno[1,2-c]pyrazol-4(1H)-one (XXVIII) yielded two isomers, which were identified by UV and NMR data, while the corresponding 3-phenyl and 3-t-butyl compounds yielded only one product. 1-Ethyl-3-substituted indeno[1,2-c]pyrazol-4(1H)-ones (XXIIa-b, XXIXb) and 2-ethyl-3-methylindeno[1,2-c]pyrazol-4(2H)-one (XXXb) underwent Grignard reaction with 3-dimethylaminopropylchloride and 4-chloro-1-methyl-piperidine to give the desired products (XXXIa-XXXIV).