Functional polyisobutylenes via a click chemistry approach

Abstract

1-(ω-Azidoalkyl)pyrrolyl-terminated polyisobutylene (PIB) was successfully synthesized both by substitution of the terminal halide of 1-(ω-haloalkyl)pyrrolyl-terminated PIB with sodium azide and by in situ quenching of quasiliving PIB with a 1-((ω-azidoalkyl)pyrrole. Azide substitution of the terminal halide was carried out in 50/50 heptane/DMF at 90 °C for 24 h using excess azide. The 1-(ω-haloalkyl)pyrrolyl-PIB precursors included 1-(2-chloroethyl)pyrrolyl-PIB, 1-(2-bromoethyl)pyrrolyl-PIB, and 1-(3-bromopropyl)pyrrolyl-PIB. In situ quenching involved direct addition of 1-(2-azidoethyl)pyrrole to quasiliving PIB initiated from 5-ferf-butyl-1,3-di(1-ehloro-1-methylethyl)benzene (bDCC)/ TiCl4 at -70 °C in hexane/CH3Cl (60/40, v/v). 1H NMR analysis of the quenched product revealed mixed isomeric end groups in which PIB was attached at either C2 or C3 of the pyrrole ring (C 2/C3 = 0.40/0.60). SEC indicated the absence of coupled PIB under optimized conditions, confirming exclusive mono-substitution on each pyrrole ring. 1-(3-Azidopropyl)pyrrolyl-PIB was reacted in modular fashion with various functional alkynes, propargyl alcohol, propargyl acrylate, glycidyl propargyl ether, and 3-dimethylamino-1-propyne, via a Huisgen 1,3-dipolar cycloaddition (Click) reaction, using Cu(I)Br/N,N,N″,N″'- pentamethyldie-thylenetriamine or bromtris(triphenylphosphine)Cu(I) as catalyst. The reactions were quantitative and produced PIBs bearing terminal hydroxyl, acrylate, glycidyl, or dimethylaminomethyl groups attached via exclusively four-substituted triazole linkages. © 2010 Wiley Periodicals, Inc.