Polyformylation of copper(II) complexes of octa-alkylporphyrins

Abstract

Vilsmeier formylation of copper(II) octaethylporphyrin (1) affords the copper(II) complexes of α-formyloctaethylporphyrin, α,γ- and α,β-diformyloctaethylporphyrins, α,β,γ-triformyloctaethylporphyrin, and α,β,γ,δ-tetraformyloctaethylporphyrin [(13), (2), (3), (14), and (15), respectively]. Similar results are obtained when copper(II) etioporphyrin-I (5) is formylated. It therefore appears that there exists no difference in regioselectivity in the diformylation reactions between the copper(II) octaethyl- and copper(II) etioporphyrin-I series. Earlier work which indicated that in the octaethylporphyrin series there is a preference for formation only of the copper(II)α,γ-diformylporphyrin (2) is suggested to be a result of preferential crystallization of the least-soluble α,γ-compound from an almost equal mixture of the two isomers.