NEW INTRAMOLECULAR ALPHA-ARYLATION STRATEGY OF KETONES BY THE REACTION OF SILYL ENOL ETHERS TO PHOTOSENSITIZED ELECTRON-TRANSFER GENERATED ARENE RADICAL CATIONS - CONSTRUCTION OF BENZANNULATED AND BENZOSPIROANNULATED COMPOUNDS

Efficient intramolecular alpha-arylation of ketones is achieved by the reaction of silyl enol ethers to photosensitized electron transfer (P ET) generated arene radical cations. The arene radical cations are gen erated by one-electron transfer from the excited state of the methoxy- substituted arenes to ground-state 1,4-dicyanonaphthalene (DCN). This arylation strategy has provided the unique opportunity of constructing five- (23), six- (18), seven- (25) and eight-membered (27) benzannula ted as well as benzospiroannulated (34) compounds. The explanation for the formation of 27 has been advanced by considering the proximity be tween the arene radical cation and silyl enol ether due to the self-co iling in the aqueous environment.