INITIATION VIA HALOBORATION IN LIVING CATIONIC POLYMERIZATION. 6. A NOVEL METHOD FOR THE SYNTHESIS OF PRIMARY AMINE FUNCTIONAL POLYISOBUTYLENES

Abstract

Polyisobutylene (PIB) benzyl amine was synthesized by reacting benzyl azide with the dichloroboron head group of PIB obtained by polymerization of isobutylene (IB) via haloboration-initia-tion with boron trichloride. The facile, one-pot reaction at room temperature resulted in quantitative conversion of the PIB dichloroboron head groups into benzyl amine functionality, determined by 1H NMR spectroscopy and titration with per-chloric acid. The hydrogenation of the secondary amine was attempted with various hydrogenation catalysts, of which only palladium yielded primary amine functional PIB. Pt and PtO hydrogenated the benzene ring resulting in PIB cyclohexyl methylene amine. With Pd only about 80% of the chain ends carried the primary amine functional group, apparently due to a side reaction. The side reaction was studied by 1H NMR spectroscopy using PIB benzyl amine prepared from deuterated IB. Although direct evidence was not obtained, the 1H NMR spectrum of the debenzylated product indicates that elimination of the amine group from the α carbon and elimination of a methyl group from the β carbon take place simultaneously, presumably due to the crowded nature of the neopentyl-type structure. The primary amine functional PIB was converted into PIB acetyl amide and imide via acylation with acetyl chloride. The products were analyzed by IR, 1H NMR, and 13C NMR spectroscopy.