Synthesis of Ester Derivatives of Brominated Poly(isobutylene-c o-isoprene):  Solvent-Free Phase Transfer Catalysis

The principles of phase transfer catalysis (PTC) are adapted to facilitate solvent-free nucleophlic substitution reactions of brominated poly(isobutylene-co-isoprene) (BIIR). Catalytic amounts of tetraalkylammonium halides are shown to activate alkali metal carboxylate salts to generate ester derivatives in moderate to high yields without incurring complications associated with ammonium carboxylate salt instability and BIIR dehydrobromination. The structures of a range of new aliphatic and aromatic allylic esters are characterized unambiguously through comparisons with products derived from brominated 2,2,4,8,8-pentamethyl-4-nonene (BPMN), which serves as a model for the reactive functionality found within BIIR. The dynamics of the intrinsic substitution process are examined along with factors that affect the rate and selectivity of phase-partitioned, solvent-free PTC systems.