THE NATURE OF ACTIVE-CENTERS IN CYCLOTRIMERIZATION OF ISOCYANATES CATALYZED BY THE TERTIARY AMINE-ALPHA-OXIDE-PROTON DONOR SYSTEM .1. THE ROLE OF THE PROTON DONOR

The rate of cyclotrimerization of phenyl isocyanate in chlorobenzene a t 120 degrees C in the presence of tile tertiary amine-alpha-oxide-pro ton donor (PD) ternary catalytic system has been studied using a dual calorimeter and a series of phenols with various acidities as the PD. In the presence of weakly acidic phenols, complexes of quaternary ammo nium type bases are formed in the ternary catalytic systems. Acidic ph enols afford salt complexes with tile transfer of a proton from phenol to the tertiary amine in a quantitative yield, while the alpha-oxide present remains unaffected. The structures of tile complexes were stud ied by IR and H-1 NMR spectroscopy.