Regioselectivity in Nickel(II)-Mediated Oxidations of Diols

Article abstract of DOI:10.1021/jo00152a013

Oxidations of 2- and 4-substituted 1,4-butanediols to their corresponding γ-butyrolactones by the combination of molecular bromine and nickel(II) alkanoate occur with a high degree of regioselectivity.The influence of the alkanoate ligand, of substituents at the 2-position of 1,4-butanediols, and of solvent on oxidation regiocontrol is examined, and comparison of regioselectivity in diol oxidations is made with representative conventional oxidative methods.Regiocontrol in nickel(II)-mediated reactions is proposed to be derived from steric constraints for oxidativehydrogen transfer to the alkanoate ligand of nickel(II) in the diol-associated complex.Alternate use of cobalt(II) alkanoates provides regiocontrol in diol oxidations that is comparable or superior to that obtained with nickel(II) alkanoates in bromine oxidations.