Condensation of methyl β-keto-cyclohexane-carboxylate with diphenyl bromomethane in boiling benzene gives rise to methyl α-diphenylmethyl-β-keto-cyclohexane-carboxylate.Hydrolysis of the keto ester with 10% alcoholic potash opens the ring to give α-diphenylmethyl-pimelic acid,the thoriwn salt of which,on pyrolysis at 400-450°,yields α-diphenyhnethyl-cyclo-hexaxione as expected.