meso-Reactivity of porphyrins and related compounds. Part 10. Direct fluorination of octaethylporphyrin with caesium fluoroxysulphate

Abstract

The reaction of octaethylporphyrin with caesium fluoroxysulphate in dioxane for a limited period at room temperature leads to meso-fluorination, the major product being 5-fluoro-octaethylporphyrin with the 5,10-difluoro, 5,15-difluoro, 5,10,15-trifluoro, and 5,1 0,15,20-tetrafluoro derivatives being formed in smaller amounts. The electronic absorption and n.m.r. (¹H, ¹⁹F) spectra of this suite of substitution products show features of considerable interest which are discussed. Caesium fluoroxysulphate appears to be a convenient source of electrophilic fluorine for aromatic substitution and, in the porphyrin series at least, its use shows some marked advantages over the multi-step Schiemann procedure.