Light-induced reactions of α-N-alkylanilino-ketones: formation of di-indolylmethanes

Abstract

Irradiation of α-N-alkylanilino-ketones, PhN(CH₂R¹)·CHR²·COMe (R¹ and/or R²= H, Me, or Ph), in methanol, propan-2-ol, or benzene caused fission of the α-carbon–nitrogen bond to give a secondary amine (PhNH · CH₂R¹), a ketone (R²CH₂·COMe), an α-[p-(alkylamino) phenyl] ketone formed by para-rearrangement, and a substituted 2-methylindole formed by ortho-rearrangement with subsequent cyclodehydration. N-Alkylanilinoacetones, PhN·CH₂R·CH₂·COMe, also yielded a di-indol-3-ylmethane derived from the 2-methylindole. Di-indolylmethanes were also formed when anilino-ketones PhN(CH₂R¹)·CHR²·COMe were irradiated together with 1,2-dimethylindole. The mode of formation of di-indolylmethanes was studied and 1 -phenylazetidinols are suggested as labile intermediates. Other anilino-ketones PhNR¹·CH₂·COR²(R¹= H, Me, or Bu^t; R²= Me, Et, Bu^t, or Ph) were also irradiated.