Highly exo‐olefinic polyisobutene synthesized using a recyclable acid

Abstract Scandium(III) and ytterbium(III) trifluoromethanesulfonate are active for the terminationless polymerization of moderate reactivity olefins (β‐pinene, isobutene, styrene) in conjunction with a variety of initiators (e.g., Brønsted acids, halogens, and carbocation synthons). Neither Lewis acid requires chlorinated/toxic solvents to operate. The Yb congener is quantitatively recovered by aqueous extraction, reactivated by dehydration, and maintains its activity after multiple reuses. Both acids produce good yields (up to ~100%) of polyisobutene with an average exo ‐olefinic end‐group content for Sc(OTf) 3 of 86% (Alfa Asear) and 75% (Aldrich), and 94% for Yb(OTf) 3 (Aldrich). The molecular weights of poly(β‐pinene) and polyisobutene made by scandium(III) and ytterbium(III) trifluoromethanesulfonate, respectively, in combination with methanol are quite favorable at ambient temperature.