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 (P-1); 2) reaction b, between (P-1), (3) and (4) to form the product (5). The rate of reaction a, () was more than the reaction b (, in acetonitrile solvent at 25 degrees C. A mechanism was proposed involving step(1) (), step(2) (k(2)), step(3) (k(3)) and step(4) (k(4)). Substituent effects with electron-withdrawing groups on para-position of benzoyl isothiocyanate (1) increased the rate constants of and k(2). The large negative entropy, Delta S-double dagger, values in reactions a, and b are in agreement with step(1) () and step(2) (k(2)), an associative mechanism with a negative Delta S-double dagger. The sum of these observations proved that the rate-determining step (RDS) is step(2). It seems that the most important steps in the reaction mechanism are step(1) () and step(2) (k(2)), which strongly control the reaction process. The kinetics and mechanism of these reactions were assessed by UV-vis spectrophotometry. [GRAPHICS] .