The aldol condensation between 2,3-diphenyl-4-thiazolidinone and aromatic aldehydes, which cannot be effected by the usual catalysts used in the analogous reactions of 2-thiono-, 2-0x0-, and 2-imino-4-thiazolidinones, was achieved by the use of ethoxide ion. The structure of the 2,3-diphenyl-5-arplidene-4-thiazolidinone was confirmed by ultraviolet spectral data.Less information is available about the 4-thiazolidinones with hydrogen or hydrocarbon substituents in the 2-position (I) than about those 4-thiazolidinones with sulphur, oxygen, or an imino group in the same position (11) (1). For example, no aldol condensation , 0, or NH) between the methylene group of I and an aromatic aldehyde has been reported, although this reaction occurs readily with all three types of compound 11. From the information available in the literature, it was uncertain whether the aldol condensation between 4-thiazolidinones (I) and aromatic aldehydes could not be effected or whether it had never been tried. Therefore, efforts were made to prepare the 5-benzylidene derivative of I.The compound chosen for study was 2,3-diphenyl-4-thiazolidinone, which is available by the reaction of mercaptoacetic acid and the Schiff base from benzaldehyde and aniline (2). When the aldol condensation of this compound with benzaldehyde was attempted using sodium acetate and acetic acid (3), or ammonia and ammonium chloride in an aqueous ethanolic solution (4), no condensation product was obtained and in each case the starting material was recovered in 88-94% yield. With anhydrous benzene as the solvent, pipe~idinium acetate as the catalyst, and a water separator attached to the reaction flask to displace the equilibrium ( 5 ) , the starting material was likewise recovered. After this work was completed, it was found that Baranov (6) had been unable to condense I (R = H ; R1 = C6H5) with carbonyl compounds such as p-dimethylaminobenzaldehyde.Presumably, he used sodium acetate in acetic acid solution to effect the condensation since these are the conditions which he had used in similar condensations.It seemed probable that the failure of the reaction was caused by the decreased reactivity of the methylene group and that a stronger base, such as ethoxide ion, would be
