Facile synthesis of 13(1)-oxo-porphyrins possessing reactive 3-vinyl or 3-formyl group, protochlorophyll-a/d derivatives by 17,18-dehydrogenation of chlorins

Methyl protopyropheophorbides-a/d were prepared by modification of readily available chlorophyll-a. The key step was oxidation of 13(1)-oxo-chlorin to the corresponding porphyrin, and 2,3-dichloro-5,6-dicyano-p-benzoquinone w as effective for 17,18-dehydrogenation. A reduction in oxidation potential of the chlorin was necessary for the oxidation. Facile oxidation was achiev ed by insertion of zinc as the central metal, reduction of the 13-carbonyl group and/or aggregation by high concentration. The synthetic 13(1)-oxo-por phyrins had vinyl and formyl groups at the 3-position. These groups were ve ry reactive in the molecule and selectively converted to other functional g roups. (C) 1999 John Wiley & Sons, Ltd.