Primary Hydroxy-Terminated Polyisobutylene via End-Quenching with a Protected N-(ω-Hydroxyalkyl)pyrrole

N -(2- tert -Butoxyethyl)pyrrole was used to end-quench TiCl 4 -catalyzed quasiliving isobutylene polymerizations initiated from 2-chloro-2,2,4-trimethylpentane and 5- tert -butyl-1,3-di(2-chloro-2-propyl)benzene at −60 °C in 60/40 (v/v) hexane/methyl chloride. End-capping was near-quantitative except for the formation of <5% exo -olefin chain ends, with alkylation occurring in both the C-3 (57%) and C-2 (38%) position on the pyrrole ring. Coupling was not observed for the monofunctional polymers; however, quenching of difunctional polymers resulted in small amounts of coupling due to dialkylation at the pyrrole ring. The terminal tert -butyl group of the N -(2- tert -butoxyethyl)pyrrole-capped polyisobutylene was rapidly and quantitatively removed in situ by addition of ethylaluminum dichloride and sulfuric acid to the reaction mixture. Furthermore, heating the reaction mixture to reflux (69 °C) forced alkylation by the residual exo -olefin chain ends and induced isomerization of the pyrrole-capped chain ends to yield exclusively [3-polyisobutyl- N -(2-hydroxyethyl)]pyrrole. The primary hydroxy-terminated polyisobutylenes showed excellent, unimpeded reactivity with carboxylic acid and isocyanates typically used in block copolymer synthesis.