Living ring-opening isomerization polymerization of 2,3,5,6-tetrahydroimidazo[2,1-b][1,3]oxazole with sulfonate initiators

Abstract

The cationic ring-opening isomerization polymerization of a bicyclic pseudourea, 2,3,5,6-tetrahydroimidazo[2,1-b][1,3]oxazole (1), was examined. The polymerization of 1 with methyl trifluoromethanesulfonate or p-toluenesulfonate proceeds even at -40°C and gives poly( 1,3-oxazolidin-2-one- 1,3-diylethylene) (2) in high yield. Postpolymerization experiments revealed that the present polymerization proceeds in a living fashion. The mechanism of the polymerization was determined from in situ 'H NMR measurements as well as kinetic analysis, which proved that the polymerization proceeds via ionic propagating species, although the apparent propagating species in the polymerization with methyl p-toluenesulfonate is covalent.