Allylic rearrangement: unusual products of bromination of N-acyl-2,2,4-trimethyl-1,2-dihydroquinolines and their use for N- and S-alkylation

Bromination of N -acyl-2,2,4-trimethyl-1,2-dihydroquinolines with N -bromosuccinimide (NBS) in CCl 4 in the presence of Bz 2 O 2 proceeded at the 4-positioned methyl group. In a DMF solution, the direction of the reaction was determined by the nature of substituent at the nitrogen atom: the reaction with one equivalent of NBS can proceed either as described above, or at position 3 with the allylic rearrangement-type migration of the multiple bond. The use of two equimoles of NBS in DMF led to 3-bromo-4-bromometh-ylene-2,2-dimethyl-3,4-dihydroquinolines. The N- and S-alkylation reactions of 3- and 4-brominated isomers resulted in the same 4- N - and 4- S -methyl derivatives.