The meso-reactivity of porphyrins and related compounds. Part IV. Introduction of oxygen functions

Abstract

Treatment of octaethylporphyrin with hydrogen peroxide in concentrated sulphuric acid in the cold gives a monoxy-derivative: the earlier structures advanced for this type of compound are disproved, and this particular example is formulated as 2,3,7,8,12,13,18,18-octaethyl-17-oxochlorin. By-products are observed, one of which is formulated as a dioxo-b-tetrahydroporphyrin. Benzoyl peroxide reacts with octaethylporphyrin in 1,2,4-trichlorobenzene at 95° to give 5-benzoyloxy-octaethylporphyrin. Hydrolysis of this gives octaethyloxophlorin, aspects of the chemistry of which are discussed. The location of the oxygen function at the meso-position is confirmed by ring synthesis.