Photocyclization of ortho-benzoyl N-alkylanilinium ions

Article abstract of DOI:10.1016/0040-4039(91)80588-W

Ortho-benzoyltrimethylanilinium tetrafluoroborate efficiently photocyclizes by triplet state δ-hydrogen abstraction to the 1,1-dimethyl-3-hydroxy-3-phenyl-2,3-dihydroindolium salt both in acetonitrile solution and as a solid. Ortho-benzoyl-N,N-dibenzylaniline hydrochloride photocyclizes in acetonitrile to N-benzyl-2,3-diphenylindole. The rate constant for δ-hydrogen abstraction is high thanks to a favorable geometry but rapid internal quenching lowers the quantum yield to only 0.02. Both reactions proceed essentially quantitatively.