Poly (substituted methylene) synthesis: Construction of polymer C-C main chain from one carbon unit

Abstract

Poly (substituted methylene) synthesis (PSMS) is a method for preparing carbon-carbon main chain polymers, where the main chain is constructed from one carbon unit. If we can find monomers and initiators suitable for the process, PSMS could be a powerful tool for polymer synthesis, providing a method for preparing C-C main chain polymers which cannot be obtained by vinyl polymerization. This review describes recent development for PSMS, particularly focusing on transition metal initiated polymerization of diazocarbonyl compounds, which can afford polymers bearing polar substituents such as ester and acyl groups on all the main chain carbons. A variety of poly (substituted methylene) s can be prepared by Pd-mediated(co) polymerization of the monomers with various substituents on their carbonyl carbons, although the molecular weights of the products are a few thousands. Pd-mediated and thermally-induced copolymerizations of diazocarbonyl compounds with alkynes and styrene, respectively, are also possible. On the other hand, Rh-mediated polymerization of ethyl diazoacetate proceeds in a highly stereospecific manner, giving syndiotactic poly(ethoxycarbonyl methylene) s with high molecular weights (Mn > 100000).