POSITIONAL REACTIVITY OF ACYLPOLYMETHYLBENZENES IN ELECTROPHILIC SUBSTITUTION

Friedel-Crafts acylation, bromination, deuteration, and nitration of a cetylpentamethylbenzene (APMB), 1-acetyl-2,3,4,6-tetramethylbenzene (A TMB), and 1-benzoyl-2,3,4,6-tetramethylbenzene (BTMB) and the resultin g product distributions were investigated. Friedel-Crafts acylation, b romination, and deuteration of APMB and Friedel-Crafts acylation of AT MB gave deacetylation-substitution products. On the other hand, bromin ation and deuteration of ATMB (or BTMB) and Friedel-Crafts acylation o f BTMB gave 5-substituted products. In both cases, the positional reac tivities were in accordance with the relative sigma-complex stability. Conversely, except for Friedel-Crafts-type nitration, the positional reactivities in the nitration of these substrates were strikingly diff erent from those of the above three reactions. Thus, side-chain functi onalization at the 6-methyl group occurred in nitration with fuming ni tric acid, depending on the solvents in use. The MNDO calculations and the reaction of APMB with single-electron transfer reagents such as t etranitromethane-hnu or cerium(IV) ammonium nitrate suggest that the p roduct distribution in nitration can be explained in terms of a single -electron transfer mechanism.