“…[19][20][21][22] More precisely, they act, for example, as inhibitors of aldose reductase, protein tyrosine phosphatase PTP, aggregation of Tau proteins, HIV-1 integrase, hepatitis C virus, protease and - In addition, they are versatile synthetic intermediates since they can undergo many chemical transformations, such as hydrolysis in basic medium to lead to mercaptoacrylic acids, 23 Michael-type addition, 24 Diels Alder reactions to access dihydropyrans 25 and 2-thioxopyrano [2,3-d] [1,3]thiazoles. 26 For these reasons, 5-arylidene rhodamines have been the subject of numerous investigations and a number of procedures have been reported for their preparation. The main method of synthesis is the Knoevenagel reaction between rhodanine and aldehydes in the presence of various catalysts, such as, for example, ammonium acetate, 27 2-hydroxyethylammonium acetate, 28 NaOAc/HOAc, 29 2,2,6,6-tetramethyl piperidine, 30 glycine, 31 1-butyl-3-methyl imidazolium hydroxide, 32 NH 4 Cl/NH 4 OH, 33 piperidine, 34 supported K 2 CO 3 on Al 2 O 3 under microwave irradiation 35 or in the presence of an ionic liquid.…”