Abstract: Polyphenylenethers are prepared by oxidative polymerization of phenols in the presence of oxygen and of organic bases (amines), by using copper-based catalysts having general formula:(B).sub.n (Cu).sub.a X.sub.b Y.sub.zwhereinB=optionally substituted naphthiridie group,X=halogen, or nitro group or perchlorate group,Y=bridge compound between the copper atoms, of the pyrazole or imidazole type,z=0 or 1, wherefore: when z=0,a and n, either like or unlike each other, are 1 or 2,b=an integer from 1 to 3, extremes included, while, when z=1:n=a=2b=3.