Oxygen mediated highly efficient cobalt(ii) porphyrin-catalyzed reduction of functional chromones: experimental and computational studies

Abstract

The highly efficient oxygen mediated reduction of functional chromones with sodium borohydride (NaBH₄) catalyzed by cobalt(II) porphyrins afforded biologically active chroman-4-ols as the reduction products in 80–98% yields. Oxygen assists in the formation of hydridocobalt(III) porphyrin as a key intermediate, which releases hydride rapidly to reduce the chromones. Additionally, the correlation between quantum calculation results of the catalysts’ conversions, yields, times and logarithms of the rate constants for the oxygen assisted reduction reaction was studied. The mechanism of the reaction was also justified by establishing a quantitative relationship between the rate constant, the α-HOMO orbital of the catalytic complex and the stabilization energy of the complex with oxygen.