The Isocyanurates. III. The Formation of Tributyl Isocyanurates from Butyl Bromides in the Presence of 1-Butanol

Abstract

Abstract The reaction of n-butyl or s-butyl bromide with potassium cyanate in dimethylformamide was carried out at 100°C for 3 hr. to give tri-n-butyl or tri-s-butyl isocyanurate. In this process, the presence of unpolymerized n-butyl or s-butyl isocyanate in the reaction mixture was detected by treating the mixture with benzylamine, thus forming 1-n-butyl or 1-s-butyl-3-benzyl urea. The presence of 1-butanol in the reaction system resulted in an increase in the yield of the corresponding isocyanurates. This tendency was remarkable when s-butyl bromide was used as a starting material. The addition of n-butyl N-n-butyl- or n-butyl N-s-butylcarbamate to the reaction system strongly accelerated the formation of isocyanurates. The acceleration due to the addition of 1-butanol described above was, therefore, attributed to the effect of carbamates formed in the reaction system. An attempt to trimerize n-butyl or s-butyl isocyanate in the presence of carbamates and dimethylthylformamide, or in the presence of carbamates and potassium cyanate, resulted in failure. Therefore, carbamates acted as strong accelerators for the trimerization of butyl isocyanates, in cooperation with basic alkali metal salts, such as potassium cyanate, in dimethylformamide.