Bromination of aromatic molecules with polymer supported reagents

Crosslinked co-poly/styrene-4-vinyl(N-hexylpyridinium bromide) was converted with bromine or chlorine to insoluble polymer supported complexes 1 or 2 respectively, and their reactivity studied in reactions with various aromatic molecules. Reagent 1 was found in all cases to be milder than reagent 2 and regiospecifically transformed alkoxy and amino substituted benzenes ( 3 ) into 4-bromo derivatives, while corresponding reactions with 2 resulted in dibromo derivatives. Several benzoheterocyclic molecules were converted with 1 to substitution or addition products, i.e. 2,3-dibromo-N-methylpyrrole, 3-bromobenzo/b/thiophene, and 2,3-dibromo-2,3-dihydrobenzofuran. In the series of ortho-alkyl disubstituted benzene derivatives, i.e. o-xylene, indane, and tetraline, where the Mills-Nixon effect was established with various electrophilic reagents, bromination reactions with 2 showed higher β-selectivity than the corresponding reactions with bromine. The rate of bromination in various alkyl substituted benzenes with reagent 2 depended on the magnitude of the alkyl group, as well as the para/ortho regioselectivity, amounting to 100% in the case of tert-butylbenzene.