N-Aryl imines fromaromaticaldehydes react in benzene with ortho-tertbutylphenoxymagnesium bromide to give 4,4′-arylidenebisphenols through two consencutive para-regiospecific processes whereas N-alkyl imines give mainly ortho-regioselective reactions in the same conditions, producing 2,2′-arylidenebisphenols .