Vitamin B-12-catalyzed allylic dimerization of some gamma- and delta -bromoalkanols with activated Zn-dust in mixture ethanol/water (1:1) has been studied. Investigated bromoalkanols were prepared from corresponding tertiary Delta (4)- and Delta (5)-alkenols by means of benzeneselenyl bromide and subjected to chemical reduction with vitamin B-12 All investigated bromoalkanols, after dehydrobromination, underwent to oxidative allylic coupling and hydratation in the presence of protic solvents to give predominantly polyhydroxy alkanols.