Photoreduction of zinc 3-acetyl-chlorophyll derivative to prepare chemically stable isobacteriochlorin

Photochemical reaction of zinc 3-acetyl-chlorophyll derivative possessing a chlorin π-system (trans-17,18-dihydroporphyrin) in the presence of a reductant in a deaerated solution gave trans-2,3-dihydrogenated products in 94% yield based on consumed starting material. The resulting photoreduced products are chemically stable and provide useful samples for investigation of isobacteriochlorins, 2,3,17,18-tetrahydroporphyrinoids.