Effect of urethane groups on the reaction of alcohols with isocyanates

Recently Reegen and Frisch reported the urethane catalysis of the alcohol–isocyanate reaction. We have made similar observations on a broader variety of reactants and catalysts including mono- and polyfunctional reactants, and tertiary amine, cobalt salt, and tin salt catalysts. We have found that the point in the reaction when urethane catalysis occurs is a function of the catalyst, the number of hydroxyl groups in the alcohol, and the effect of the interaction of the catalyst, alcohol, and isocyanate on the geometry of the reactive complex.