Synthesis of tetrahydroindazol-4(5H)one and 7-thione from reaction of functionalized cyclic enaminones with hydrazine

Abstract

Functionalized enaminones; 3-N-(aryl)amino-1--oxo-cyclohex-2-ene-2-dithiocarboxylates cyclohex-2-en-1-ones and 3-N-(aryl)amino-2-(N-aryl)thioamido-cyclohex-2-en-1-ones were obtained upon reaction of 3-N(aryl)amino-5,5-dimethyl-1-oxo-cyclohex-2-enes with carbon disulfide in presence of sodium hydroxide in DMSO, followed by methylation with dimethyl sulfate or with phenyl and p-bromophenyl isothiocyanates in toluene or under solvent-free condition, respectively. The cyclization of the dithioesters or the thioamides with hydrazine hydrate was accompanied by a displacement of the 3-N- arylamine moiety by a hydrazine group to give 6-hydrazino-4,4-dimethyl-1,3,4,5-tetrahydroindazole-7-thione or 3-N-(aryl)amino-4,5,6,7-tetrahydro-1H-indazole-4(5H)one respectively. Structure of the indazole derivatives formed was further confirmed from their reaction with acetone or p-nitrobenzaldehyde. The new structures were confirmed using 1HNMR, 13CNMR, 2DNMR, DEPT experiments and mass spectra.