Orthogonal C–B Bond Transformation as an Approach for Versatile Synthesis of End-Functionalized Polymers
journal contributionposted on 2022-05-04, 17:13 authored by Tomoaki Kanazawa, Tsuyoshi Nishikawa, Makoto Ouchi
Conventionally inaccessible end-functionalized vinyl polymers were synthesized via orthogonal side-chain replacement for terminal and repeating units of poly(alkenyl boronate)s. A terminal-defined polymer of isopropenyl boronic acid pinacol ester (IPBpin) was synthesized via RAFT polymerization, and subsequent cobalt (Co)-catalyzed end olefination afforded the polymer carrying the C(sp2)–B bond at the terminal and the C(sp3)–B bond in repeating units. Herein, the terminal C(sp2)–B bond was selectively transformable via palladium (Pd)-catalyzed Suzuki-Miyaura cross coupling, and subsequent transformation of the repeating C(sp3)–B unit gave the poly(α-methyl vinyl alcohol) [poly(MVA)] bearing various functional groups at the terminal. The boron-based stepwise polymer reaction thus overcame the synthetic difficulty of the end-functionalized poly(MVA), which is ascribed to the poor polymerization ability of the corresponding acetate monomer, i.e., isopropenyl acetate.