Synthesis of Polyethylene with In‐Chain α,β‐Unsaturated Ketone and Isolated Ketone Units: Pd‐Catalyzed Ring‐Opening Copolymerization of Cyclopropenone with Ethylene

• Published in: Angewandte Chemie International Edition 2019-09, Vol.58 (37), p.12955-12959
• Main Authors: Wang, Xiaoming, Seidel, Falk William, Nozaki, Kyoko
• Format: Article
• Language: English
• Subjects: Alkenes; Carbonyl compounds; Carbonyl groups; Carbonyls; Chains; Coordination; Copolymerization; Ethylene; Functional groups; Ketones; Monomers; Palladium; Polyethylene; Polyethylenes; polymers; Polyolefins; Ring opening polymerization; small ring systems; structure elucidation; Transition metals
• ISSN: 1433-7851; 1521-3773
• DOI: 10.1002/anie.201906990

Although various functionalized units can be incorporated into polyolefins by transition metal catalyzed coordination copolymerizations of nonfunctionalized olefins with polar functional monomers, the incorporated functional units are largely limited to a C1 unit from either CO or C2 units from vinyl monomers. Reported here is the Pd‐catalyzed copolymerization of ethylene with cyclopropenone, leading to incorporation of C3 units with functional groups, α,β‐unsaturated ketones, in the chain. Coordination‐insertion of the carbonyl group and ring opening of the strained three‐membered ring are proposed as the key steps in the mechanism. Under different reaction conditions an isolated ketone structure was afforded as the major carbonyl unit, and could be generated by the copolymerization of ethylene with CO formed in situ from cyclopropenone. Daisy chain: A C3 polar monomer unit was successfully incorporated into a polyethylene chain for the first time by the Pd‐catalyzed copolymerization of cyclopropenones with ethylene. A polyethylene‐containing α,β‐unsaturated ketone unit in the chain was obtained, possibly by coordination‐insertion of the carbonyl group and ring opening of the strained three‐membered cyclopropenone ring. Under different reaction conditions, an isolated ketone structure was afforded as the major carbonyl unit, and was generated by the copolymerization of ethylene with CO formed in situ from cyclopropenone.