Catalyst-free synthesis of (7 E )-7-benzylidene-3,3a,4,5,6,7-hexahydro-2,3-diphenyl-2 H -indazole derivatives in PEG-400 as a green and reusable solvent

Abstract

The reaction of 2,6-bisbenzylidenecyclohexanones and phenylhydrazine in polyethylene glycol (PEG)-400 as a green and reusable solvent under catalyst-free conditions gave hexahydroindazoles as the major product and, in some cases, tetrahydroindazoles were also produced as a minor product. The products were easily separated by simple recrystallisation. The structures of the indazoles were confirmed using FTIR and NMR spectroscopy. Two X-ray structures are reported.