A facile synthesis of cyano-chlorins related to chlorophyll from formyl (pyro)-pheophorbide-a by a tandem transformation of the aldehyde into a nitrile group

A facile synthesis for cyanochlorin related to chlorophyll from a formyl-substituted chlorin, by the oxidation of methyl(pyro)pheophorbide-a, was accomplished. These readily available chlorin aldehydes were assembled together with hydroxylamine hydrochloride in a tandem process to produce the corresponding chlorin nitriles in moderate to good yields. The formation of chlorin nitrile was discussed and a possible mechanism for the corresponding cyanation reaction was tentatively proposed.