Catalysis of the combined formation of urethanes, allophanates, and isocyanurates by sodium compounds

A mechanism was established for the polyaddition of phenyl isocyanate in the presence of methanol and sodium compounds, differing in anion nucleophilicity. Experimental evidence is given for two reaction pathways: continuous anionic cyclotrimerization of phenyl isocyanate and anionic polymerization of phenyl isocyanate with termination at the corresponding proton donors.