A short route to chlorin-α-diones

Chlorin-α-diones and tetraones are useful intermediates for the formation of porphyrin arrays. We have developed a simple three-step route to chlorin-α-diones and tetraones. It was found that meso-tetraarylchlorins could be converted to hydroxychlorins when adsorbed on silica. The hydroxychlorins could then be oxidized with the Dess-Martin Periodinane to the corresponding chlorin-α-diones and tetraones. The parent 5,10,15,20-tetrakis(3,5-di-t-butylphenyl)porphyrin could be transformed to 17,18-dioxo-5,10,15,20-tetrakis(3,5-di-t-butylphenyl)chlorin in the three steps in an overall yield of 54% while a tetraazaanthracene linked bis-bacteriochlorin could be transformed to the bis-bacteriochlorin-tetraone in a yield of 16%.