Cyclization kinetics and mechanism of N-benzoyl-N'-(1,2-dimethyl-3-oxo-1-butenyl)thiourea

Abstract

Cyclization kinetics of N-benzoyl-N'-(1,2-dimethyl-3-oxo-1-butenyl)thiourea have been studied in aqueous and methanolic solutions of acids and bases. In all cases the cyclization product is 4,5,6-trimethyl-2,5-dihydro-2-thioxopyrimidine or its protonated or deprotonated forms. In dilute methanolic and aqueous hydrochloric acid the substrate reacts in its monoprotonated form. The cyclization in basic media is catalyzed by methoxide or hydroxyl ion and also by primary and secondary amines at such pH values where the catalysis by lyate ion is practically insignificant. Tertiary amines and acetate ion do not catalyze the cyclization.