Reduction of 2,3,4,5-tetraphenylcyclopentadienone (tetracyclone)

A convenient route for the reduction of tetracyclone (1) to 1,2,3,4-tetraphenylcyclopentadiene (2) is to heat a mixture of 1, hydrazine hydrate (excess), and hydrazine dihydrochloride in diethylene glycol for 4 h. In the absence of the solvent diethylene glycol the product obtained was shown from the IR, NMR and mass spectral data to be the enone 3.