Oxygenation of Olefins under Reductive Conditions. Cobalt-Catalyzed Selective Conversion of Aromatic Olefins to Benzylic Alcohols by Molecular Oxygen and Tetrahydroborate

Article abstract of DOI:10.1021/jo00183a020

A high-yield catalytic conversion of aryl olefins 1 to benzylic alcohols 2 was developed by the use of molecular oxygen and BH4^- in the presence of a catalytic amount of Co(TPP).Acid-labile alcohols were prepared in good yields.The reaction was regioselective to give benzylic alcohols exclusively and nonstereoselective.Comparison of the results of the catalytic oxygenation of styrene, the stoichiometric oxygenation of alkylcobalt complex 6, and the decomposition of 1-phenylethyl hydroperoxide (7) in distribution of products and deuterium incorporation at room and low temperatures indicated the participation of 7 as the primary product, which is formed by the reaction of 6 with molecular oxygen.Co(TPP) catalyzed three elementary reactions in the overall catalytic process: formation of 7, decomposition of 7 to 2 and aryl ketone 5, and reduction of 5.