Kinetic analysis of new multi-component reaction for the formation of Z-N-(3-(naphthalene-2-yl)-4-oxothiazolidine-2-ylidene) benzamide

A new three-component reaction was studied kinetically among benzoyl isothiocyanate (1), 1-naphthylamine (2), and methyl bromoacetate (3) in the presence of triethylamine (4) as a catalyst, to yield Z-N-(3-(naphthalene-2-yl)-4-oxothiazolidine-2-ylidene) benzamide (5). The overall reaction is a combination of two reactions; 1) reaction a, between (1) and (2) forming 1-benzoyl-3-(naphthalen-1-yl) thiourea (P1); 2) reaction b, between (P1), (3) and (4) to form the product (5). The rate of reaction a, (kobsa=66.49 M1 min1) was more than the reaction b (kobsb=2.9 M1 min1), in acetonitrile solvent at 25 °C. A mechanism was proposed involving step1 (kobsa), step2 (k2), step3 (k3) and step4 (k4). Substituent effects with electron-withdrawing groups on para-position of benzoyl isothiocyanate (1) increased the rate constants of kobsa and k2. The large negative entropy, ΔS, values in reactions a, and b are in agreement with step1 (kobsa) and step2 (k2), an associative mechanism with a negative ΔS. The sum of these observations proved that the rate-determining step (RDS) is step2. It seems that the most important steps in the reaction mechanism are step1 (kobsa) and step2 (k2), which strongly control the reaction process. The kinetics and mechanism of these reactions were assessed by UV–vis spectrophotometry.