Solvent-free condensation of cyclohexanone (1) and diethyl succinate (2) in
the presence of (BuOK)-O-t at room temperature gives cyclohexylidenesuccin
ic acid (3), while heating a mixture of 1, 2 and (BuOK)-O-t at 80 degreesC
gives only cyclohexenylsuccinic acid (4).