The present paper reports copolymerizations of two cyclic imino ethers, 2-oxazoline (OZO) and 5,6-dihydro-4£f-1,3-oxazine (OZI), with two cyclic carboxylic anhydrides, succinic anhydride (SAn) and glutaric anhydride (GAn). The copolymerizations took place spontaneously around room temperature to 100 °C to produce 2:1 sequence-regulated copolymers (1). This result was explained by the concept of "no catalyst alternating copolymerization via zwitterion intermediate". Thus, OZO and OZI behaved as nucelophilic monomers (Mn) whereas SAn and GAn acted as electrophilic monomers (ME). First, a 1:1 bicyclic adduct (such as 3, 6, and 7) is formed by the reaction between MN and ME. Then the cyclic adduct behaved as ME to react with another molecule of MN, giving rise to a zwitterion like 5, a key intermediate for the copolymerization, which has a 2:1 MN/ME composition. Subsequent reactions of these key intermediates led to the production of 2:1 sequence-regulated copolymers 1.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.