A study on the oxidation of 2-hydroxyporphyrins to porphyrin-α-diones

Abstract

Porphyrin-α-diones have been used for the preparation of extended rigidly oriented porphyrin systems. Copper 2, free-base 3, and zinc 4 2-hydroxyporphyrins have been prepared by an improved method and treated with a range of oxidants to form the corresponding porphyrin-α-diones, 5, 6, and 7 in yields of up to 94%. We have found that the free-base 2-hydroxyporphyrin 3 was easily oxidised and usually gave the best yields of porphyrin-α-dione. In this study the most effective general oxidant was determined to be the Dess–Martin periodinane which oxidised all three 2-hydroxyporphyrins to their respective porphyrin-α-diones in good yields.