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 But; R2= Me, Et, But, or Ph) were also irradiated.