Pd(0)-catalyzed polycondensation of methyl propargyl carbonate and bisphenols under stoichiometrically imbalanced conditions

We found that a novel Pd(0)-catalyzed polycondensation of methyl propargyl carbonate (1) and bisphenol analogs 4 such as 4,4'-dihydroxydiphenyl ether (4b) proceeded successfully and gave polyethers 5 having exomethylene groups. The polycondensation was affected by the kind of bisphenol analogs used. The molar ratio of 1 and 4 also affected the polymerization behavior. Polyethers 5 with higher molecular weights were obtained by polymerization with 0.5 equiv of 4 toward 1. The use of 1 equiv of 4 gave poor results. When 4,4'-dihydroxybenzophenone (4d) was employed as a nucleophile, benzenesulfonamide (13) was needed as an additive for obtaining the corresponding polyether with higher molecular weight. The Pd(0)-catalyzed condensation of 1 and p-hydroxyacetophenone was conducted as a model reaction. The desired compound and three by-products were produced. Two of the by-products were formed by reaction of 1 and methanol liberated from 1. The other one appeared to be formed via hydrogenolysis. The formation of the by-products suggested that some terminal reactions took place in the polycondensation of 1 and 4.