Repetitive sp³−sp³ Carbon−Carbon Bond-Forming Copolymerizations of Primary and Tertiary Ylides. Synthesis of Substituted Carbon Backbone Polymers:  Poly(cyclopropylidine-co-methylidine)

Abstract

We report a repetitive sp 3 -sp 3 carbon-carbon bond-forming polymerization for the controlled synthesis of cyclopropyl containing carbon backbone polymers with tailored end groups and molecular weight. Poly(cyclopropylidine-co-methylidine) copolymers (10) were synthesized via copolymerization of (dimethylamino)tolyloxosulfonium cyclopropylide (11) with dimethylsulfonium methylide (8). The polymer was synthesized in M n ranges from 1800 to 6714. The cyclopropyl:methyl incorporation ratios varied from 1:12 and 1:18. The composition of the poly(cyclopropylidine-co-methylidine) polymer ( 10) was established by NMR and IR. GPC revealed a monomodal distribution with PDI between 1.06 and 1.28. The cyclopropyl groups extend the range of functionality that can be incorporated into carbon backbone polymers and illustrate for the first time the use of tertiary ylides as monomers for the polymerization reaction. Direct control of the amount of cyclopropyl groups in the carbon backbone has potential for selective modification of the polymer by, for example, radical ringopening reactions to create new topologies and cross-linking opportunities.

Polymethylene‐Based Copolymers by Polyhomologation or by Its Combination with Controlled/Living and Living Polymerizations

“…The cyclopropyl group has also been successfully introduced into a PM chain through copolyhomologation of the primary ylide a and the tertiary ylide e (Scheme ) . The two ylides were alternatively added into the polymerization solution with an interval of 4–6 min.…”

“…Dimethylsulfoxonium methylide, synthesized from trimethylsulfoxonium chloride and sodium hydride, was first used in polyhomologation with triethylborane (BEt 3 ) as initiator to produce well‐defined PMs (Scheme ) . Some substituted methylides have also been used in polyhomologation (Scheme ) . The reactivity of ylide strongly depends on the environment of the carbanion.…”

“…Primary ylides such as dimethylsulfoxonium methylide a and its deuterated derivative b , as well as (dimethylamino)phenylsulfoxonium methylide c are active monomers for the polyhomologation. In the case of substituted ylides, such as (dimethylamino)phenylsulfoxonium ethylide d and (dimethylamino)‐ p ‐tolyloxosulfoxonium cyclopropylide e , the polyhomologation does not occur due to the high steric hindrance around the zwitterionic complex, which prevents the migration and addition reactions needed to form polymethylene . The polymerizability of ylides can be ranked according to the relative steric hindrance around the carbanion: primary > secondary > tertiary ylide.…”

“…[ 21 ] Some substituted methylides have also been used in polyhomologation (Scheme 2 ). [ 13,[22][23][24][25][26][27] The reactivity of ylide strongly depends on the environment of the 1.06 to 1.28 have been prepared in yields ranging from 30% to 54%. The content of the cyclopropyl groups from polyhomologation of the tertiary ylide e was less than expected (8.3% by NMR instead of the theoretical value of 16.7%).…”

“…In the case of substituted ylides, such as (dimethylamino)phenylsulfoxonium ethylide d and (dimethylamino)-p -tolyloxosulfoxonium cyclopropylide e , the polyhomologation does not occur due to the high steric hindrance around the zwitterionic complex, which prevents the migration and addition reactions needed to form polymethylene. [ 23 ] The polymerizability of ylides can be ranked according to the relative steric hindrance around the carbanion: primary > secondary > tertiary ylide. Although the latter ylides failed to homopolymerize, they are able to copolymerize with primary ylides and give rise to the corresponding random copolymers.…”