Highly cis-1,4 Selective Living Polymerization of Unmasked Polar 2-(2-Methylidenebut-3-enyl)Furan and Diels-Alder Addition.

The polymerization of a new polar diene-based monomer 2-(2-methylidenebut-3-enyl)furan (MBEF) without masking is achieved by using the bis(phosphino)carbazoleide-ligated yttrium (Y) alkyl complex upon the activation of [Ph3 C][B(C6 F5 )4 ]. Under mild conditions, the polymerizations under the monomer-to-Y ratios ranging from 100:1 to 500:1 perform fluently in high yields. The afforded polydienes bearing pendant terminal furan groups have high cis-1,4-regularity up to 98.6% and molecular weights close to the theoretic values and narrow polymer dispersity index(PDI) (1.13-1.17) suggesting a livingness polymerization mode. In addition, this novel polydiene is an excellent building block for preparing functional rubber materials. For example, via Diels-Alder addition of furan groups under mild conditions, hydroxyl groups are successfully introduced on the side chains efficiently in a 75% conversion. Furthermore, the copolymerization of polar MBEF and nonpolar isoprene is also successfully realized by the bis(phosphino) carbazoleide-ligated scandium analog to access furan-modified cis-1,4 (>97%) polyisoprene with different MBEF contents (5.3%, 8.7%).