OXIDATIVE CARBONYLATION OF ALIPHATIC MONOAMINES, DIAMINES, AND TRIAMINES CATALYZED BY MONTMORILLONITE BIPYRIDINYLPALLADIUM(II) ACETATE

A simple, efficient, and highly selective non-phosgene route has been developed for the preparation of aliphatic, alicyclic, and/or aromatic mono-, di-, and triurethanes from the corresponding amines using montmorillonite-bipyridinylpalladium(II) acetate (Pd-Clay) in the presence of NaI as a promoter. The catalytic activity of other palladium catalysts was studied and compared with Pd-Clay. The difference in reactivity, as well as the selectivity between the immobilized palladium catalyst, i.e., Pd-Clay, and the homogeneous catalyst systems is accounted for in terms of the position and the electronic environment of the metal in the interlayers of the clay system surrounded by the surface Bronsted acidic sites. The versatility of the present catalytic system was demonstrated by the synthesis of commercially important isocyanate precursors, including those of Dytek-A-diurethane and isophorone diurethane.