ORGANIC-PHOTOCHEMISTRY .21. 9H-CYCLOPENTA[B][1] BENZOSELENINE - NEW HETEROCYCLIC RING-SYSTEM

By way of a photo‐induced selenolester‐seleninone rearrangement, the derivative 5 of a new heterocyclic ring system, 9H‐cyclopenta[b][1]benzoselenin, has been formed. This rearrangement occurs via a new photosubstitution reaction of S‐aryl‐ in competition with Se‐aryl‐groups, followed by photocyclization using 2‐p ‐tolythiocyclopentene ‐1 ‐ selenocarbonic acid Se‐p‐tolylester (1a) as starting materials. As a competing product in this photo‐rearrangement, a second heterocycle, 7‐methylcyclopenta[b] [1]benzothiopyrone (4) (9) has been formed via an intramolecular photochemical Friedel Crafts reaction. Copyright © 1979 Journal of Heterocyclic Chemistry