A computational study of base-catalyzed reactions between isocyanates and epoxides affording 2-oxazolidones and isocyanurates

Title reactions were investigated with ab initio calculations. Methyl isocy anate and ethylene oxide were adopted as model reactants. The products, 2-o xazolidones and isocyanurates, cannot be yielded without a base catalyst. T he 2-oxazolidone may be produced by a dual S(N)2 reaction, where the cataly st base (e.g., Cl-) is a nucleophile and a leaving group on the ethylene-ox ide carbon. Isocyanurate is generated by the stepwise association of three isocyanate molecules, where one of the molecules is initially linked with a base. The six-membered ring isocyanurate is isomerized stepwise into the c omponents isocyanate and 2-oxazolidone. A tetrahedral type of complex betwe en the isocyanurate and a base-catalyzed ethylene oxide is the key intermed iate for the isomerization. (C) 2001 John Wiley & Sons, Inc.