EXPLORATORY STUDIES OF ALPHA-SILYLAMINO AND ALPHA-SILYLAMIDO 2,5-CYCLOHEXADIEN-1-ONE SET PHOTOCHEMISTRY - METHODOLOGY FOR SYNTHESIS OF FUNCTIONALIZED HYDROISOQUINOLINES

The electron-transfer (SET) photochemistry of selected alpha-silylamino and alpha-silylamido 2,5-cyclohexadienones has been explored with the intent of developing a novel and potentially efficient method for functionalized hydroisoquinoline synthesis. These substances, prepared by Birch reduction-alkylation-oxidation sequences, were found to undergo 9,10-dicyanoanthracene-SET-sensitized radical cyclization to form hydroisoquinolines in a highly regio- and stereoselective fashion and in modest to good yields. In contrast, the major direct irradiation reaction pathway followed by the alpha-silylamido-substituted systems involves type A rearrangement to bicyclic cyclohexenones or phenols. Direct irradiation of the alpha-silylamino analogs, on the other hand, brings about near-exclusive conversion to the corresponding hydroisoquinolines. The synthetic and mechanistic features of this study are described.