Bromination of aromatic molecules with polymer supported reagents

✍ Scribed by Barbara Zajc; Marko Zupan

• Book ID: 104203510
• Publisher: Elsevier Science
• Year: 1989
• Tongue: French
• Weight: 617 KB
• Volume: 45
• Category: Article
• ISSN: 0040-4020
• DOI: 10.1016/s0040-4020(01)85800-2

✦ Synopsis

Crosslinked co-poly/styrene-4-vinyl(N-hcxylpyridinium bromide) was converted with bromine or chlorine to insoluble polymer supported complexes I 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 (3J into 4-bromo derivatives, while corresponding reactions with z 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 p-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 padortho regioselectivity, amounting to 100% in the case of tert-butylbenzene.