Polymerization of 2,7,8-trioxabicyclo[3.2.1]octane and 2,8,9-trioxabicyclo[3.3.1]nonane

Treatment of 2,7,8-trioxabicyclo [3.2.1] octane (I) with electrophilic initiators gave polyorthoester composed of five- (70-86%), six-, and seven- (the sum, 14-30%) membered rings. Treatment of 2,8,9-trioxabicyclo [3.3.1]nonane (VI) with electrophilic initiators gave mainly oligomers. Trifluoromethane sulfonic acid in dichloromethane was particularly effective for the formation of dimer, 2,8,10,16,17,18-hexaoxatricyclo[11.3.1.1]hexadecane. The analysis of the structures of poly-I and oligomer-VI suggests that I and VI are polymerized through an S_N1 mechanism.