Regioselective Condensation Polymerization of Propargylic Electrophiles Enabled by Catalytic Element-Cupration

Abstract

Here, we report a set of new polymerization reactions enabled by the 1,2-regioselective hydro- and silylcupration of enyne-type propargylic electrophiles. Highly regioregular head-to-tail poly(2-butyne-1,4-diyl)s (HT-PBD), bearing either methyl or silylmethyl side chains, are synthesized for the first time. A rapid entry into carbon-rich copolymers with adjustable silicon content is developed via in situ monomer bifurcation. Furthermore, a one-pot polymerization/semireduction sequence is developed to access a cis-poly(butadiene)-derived backbone by a ligand swap on copper hydride species. Interestingly, borocupration, typically exhibiting identical regioselectivity with its hydro- and silyl analogues, seems to proceed in a 3,4-selective manner. Computational studies suggest the possible role of the propargylic leaving group in this selectivity switch. This work presents a new class of regioregular sp-carbon-rich polymers and meanwhile a novel approach to organosilicon materials.