Intra- vs inter-molecular electron transfer processes in C[sbnd]N bond forming reactions. Photochemical, photophysical and theoretical study of 2′-halo-[1,1′-biphenyl]-2-amines

Abstract

N-Arylation reaction is obtained when 2′-halo-[1,1′-biphenyl]-2-amines are irradiated in basic medium. On the basis of photochemical, photophysical experiments and computational studies we propose that carbazoles are formed by intermolecular electron transfer via SRN1 mechanism. In general, biphenylamines with an EDG like Me or OMe behave in the same way as H giving both, cyclized and reduced products. On the other hand, biphenylamines containing EWG like CN, COOEt or CF3gave only the corresponding carbazole. Herein, we report for the first time the chain length for the propagation cycle of intramolecular SRN1 reactions and explain that differences in the distribution of products suggest differences regarding the overall mechanism involved.