Cationic polymerization of methoxyallene with Lewis acids

The cationic polymerization of methoxyallene (1) was carried out with some Lewis acids at −50°C in dichloromethane. BF3OEt2 was found to be an effective catalyst for the cationic polymerization of 1. From analyses of 1H and 13C NMR spectra, the obtained polymers consist of units with the 1,2‐double bond of 1 being opened, although the 2,3‐double bond is consumed also to an amount of 24 to 43 mol‐%. This decrease in 2,3‐double bond content in the polymer may be attributed to intramolecular cyclization of the propagating cation and/or the intermolecular reaction of the propagating cation with polymer to produce a graft polymer. Moderately polar solvents such as dichloromethane proved to be best suited for obtaining polymers with high double bond content.