1) The Knoevenagel condensation of aldehyde (I) with rhodanine (II) using NH4OAc and AcOH afforded benzylidene- thiazolidine (III). The methyl ester group of (III) was hydrolyzed with HCl in AcOH, and the resulting carboxylic acid (IV) was coupled to 4-(trifluoromethyl)benzylamine (V) in the presence of diethyl phosphorocyanidate and Et3N to produce amide (VI). Subsequent hydrogenation of the olefinic double bond of (VI) over Pd/C provided the target benzylthiazolidine.

2) An alternative method starting from aniline (VII) employed the Meerwein arylation of methyl acrylate (IX) with the intermediate diazonium salt (VIII) in the presence of cuprous oxide. The resulting bromoester (X) was cyclized with thiourea (XI) in Et2O, followed by hydrolysis with HCl in sulfolane to afford (XIII). Finally, acid (XIII) was coupled to benzylamine (V) in the presence of (EtO)2POCN and Et3N.