Thiazolidin-4-one formation. Mechanistic and synthetic aspects of the reaction of imines and mercaptoacetic acid under microwave and conventional heating

Abstract

Microwave irradiation of a mixture of benzylidene-anilines and mercaptoacetic acid in benzene gives 1,3-thiazolidin-4-ones in very high yield (65-90%), whereas the same reaction performed through using the conventional method, at reflux temperature, requires a much longer time and gives a much lower yield (25-69%). This difference seems to be due to some intermediates and by-products formed during the conventional reaction. On the basis of 1H NMR studies, two different mechanisms, acting in benzene and in DMF, respectively, have been hypothesized for the thiazolidin-4-one system formation.

A Preliminary Study on Predicting the 13c Chemical Shifts for a Series of Disubstituted 2,3-Diphenyl-1,3-Thiazolidin-4-Ones

“…1 " 5 It should be pointed out that the most popular method of synthesizing the substituted diphenyl-l, 3-thiazolidin-4-ones, shown in Scheme 1, is by the reaction of the appropriately substituted imine with thioglycollic acid. 6 ' 7 However, this method does not always result in the desired product.…”

“…9 Recently, evidence of oxazolidione formation has been shown as a side reaction in the process. 6 Attempts to use hydroxylated aldehydes for imine formation by treatment with substituted anilines result in polymeric products. 10 Having a method for predicting the C-2, C-4 and C-5 resonances, in advance of synthesis, would aid in a quick confirmation of the desired product.…”

Synthesis and spectral data of new 1,2-bis-(2-hetaryl-4-oxothiazolidin-3-yl)ethanes and 1,4-bis-(2-hetaryl-4-oxothiazolidin-3-yl)butanes

“…However, a one-pot three-component reaction of amine, aldehyde and mercaptoacetic acid is recently emerged as an efficient synthesis of 4-thiazolidinones [15][16][17][18]. In both cases the reaction is believed to proceed first via an imine formation followed by attack of sulphur nucleophile on the imine carbon and finally intramolecular cyclization with loss of a molecule of water [19,20]. Little is known about α,ω-bis-(2-hetaryl-4-oxothiazolidin-3-yl)alkanes [1][2][3][4].…”

Microwave-Assisted Synthesis of 1,3-Thiazolidin-4-ones and 2-Aryl-1,3-oxathiolan-5-ones

“…These compounds have been previously prepared from three components (an aldehyde, an amine and mercapto acetic acid), by various one-and two-step syntheses [1]. Such reactions have also been carried out using microwave irradiation [5,6]. The reactions proceed by initial imine formation, which undergoes attack by the sulfur nucleophile, followed by intramolecular cyclization on elimination of water.…”