The meso-reactivity of porphyrins and related compounds. Part II. Halogenation

Abstract

The α-chloro-, αγ-dichloro-, and αβγδ-tetrachloro-derivatives of octaethylporphyrin have been prepared by direct halogenation of the porphyrin. Chlorination of octaethylchlorin gives the corresponding γ-chloro- and γδ-dichloro-chlorins; dehydrogenation of the former with 2,3-dichloro-5,6-dicyanobenzoquinone leads to α-chloro-octaethylporphyrin. α-Bromo-octaethylporphyrin has been obtained in an analogous way, but attempts to brominate octaethylporphyrin directly, and to iodinate either octaethylporphyrin or octaethylchlorin, have been unsuccessful. The nuclear magnetic resonance and electronic spectra of the meso-halogenoporphyrins are presented and discussed.