Rhodaninic acid

To the rhodaninic acid of Nencki (22), for which he proposed formula 39. 

In 1877, Nencki (22) condensing ammonium thiocyanate with chloroacetic acid, attributed the name rhodaninic acid (Rhodaninsaure) to the compound he obtained. He noted the ability of rhodaninic acid to give colored derivatives with ferric salts. 

In 1879, Liebermann and Lange (20) demonstrated the formula of rhodaninic acid to be 39. 

In 1884, Nencki (70), studying the properties of rhodaninic acid, confirmed the formula proposed by Libermann and Lange (39) and noted its ability to condense with aldehydes. 

In 1887 (57) and 1889 (73) Andreasch confirmed the cyclic formula proposed by Liebermann and Lange (20). Freydl (74) obtained rhodaninic acid by condensing thioglycolic acid with thiocyanic acid. 

Rhodanines, as intermediates, in synthesis of amino adds peptides and purines, 167 Rhodaninic acid, see 2-Mercapto-4-hydroxy-thiazole Rhodanine Rhodanine, modes of preparation, 19 /V-phenyl, preparation, 19 /V-substituted, preparation, 20 structure of, 19... 

S-substituted, preparation, 20 Rhodaninic acid, see 2-Mercapto-4-hydroxy-thiazole Rhodanine... 

Substituted rhodaninic acids and their aldehyde condensation products... 

Rhodanic acid Rhodaninic acid Rodanin 2,4-Thiazolidinedione, 2-thio-4-Thiazolidinone, 2-thioxo- 2-Thio-4-ketothiazolidine 2-Thio-2,4-thiazolidinedione 2-Thioxo-4-thiazolidinone Empirical C3H3NOS2... 

Merocyanines belong to the class of nonionic methine dyes combining two nuclei, one of which is a ketomethylene of acidic nature such as pyrazolone, rhodanine, oxazolone, thiohydantoin,. 

Among the thiazole derivatives known for a long time, but whose structure was not at once acknowledged as such, leading to some controversies, are so-called thiocyanoacetic acid, thiohydantoine, rhodanine, mercaptothiazole, and sulfuvinuric acid. 

In 1902, Wheeler and Johnson (63) obtained 5-substituted rhodanines (54) by condensing substituted bromornalonic esters with postassium thiocyanate, then thiolacetic acid, the cydization resulting from an alkaline treatment. 

In 1908, Korner (77) developed the synthesis of N-substituted rhodanines (55) from dithiocarbaminacetic acid ... 

During a relatively long period, the condensation of rhodanines with aldehydes was developed, especially by Andreasch s group (78-87). Finally, Holmberg (88, 89) described the best method to obtain rhodanines the condensation of ammonium dithiocarbamate with a sodium or potassium salt of an a-chloro acid. 

Rhodanine (2-mercaptothiazolidin-4-one) 5.18. Crystd from glacial acetic acid or water. 

Other analytical assays proposed for the quantification of hydrolyzable tannins in plant materials include the rhodanine assay for the estimation of gallotannins (Berardini and others 2004) and sodium nitrate for the quantitative determination of ellagic acid (Wilson and Flagerman 1990). 

Heating the first-obtained product in a strong acid leads to the hydrolysis of the ester. The resulting (3-ketoacid loses carbon dioxide under reaction conditions the acetal hydrolyses also reveal the free aldehyde (106-6). Aldol condensation of this last intermediate in the presence of a base with readily available rhodanine (106-7) links the two fragments. The double bond in the first-formed product is then reduced catalytically to afford darglitazone (106-8) [117]. 

A variety of heterocyclic systems have been used for forming merocyanines. The more usual nitrogen-containing heterocycles involved include benzimidazole, quinoline, ben-zothiazole, benzoselenazole, thiazole, thiazoline and indolenine. Among the more useful carbonyl-containing heterocycles are derivatives of 2-pyrazolin-5-one, 2-thiobarbituric acid, rhodanine and hydantoin. 

Condensation of formyl-pyrroles and -indoles with a wide range of other activated methylene compounds has been reported. These include, for example, hydantoin, which provides a useful synthetic route to tryptophane and j8- (pyrrolyl)alanines, thiohydantoin, rhodanine and AT-substituted barbituric acids (B-77MI30505, 79HC(25-3)357). Flash pyrolysis of the condensation product derived from 3-formyl-2,5-dimethylpyrrole with Meldrum s acid produces 6-hydroxy-2-methylindole, (440) — (441) (74AJC2605), whilst the analogous... 

Pentafluoro-, 2,3,5,6-, 2,3,4,6- and 2,3,4,5-tetrafluorobenzaIdehyde readily form benzylidene derivatives with rhodanine.110 The products are hydrolyzed by base to /3-aryl-a-mercaptoacrylic acids, which cannot be isolated, but which spontaneously cyclize by nucleophilic displacement of fluorine to give 4,5,6,7-tetrafluoro- and 4,5,7-, 4,6,7-and 5,6,7-trifluorobenzo[6]thiophene-2-carboxylic acid, respectively. 

Benzo[6]thiophene aldehydes have been condensed with a variety of active methylene compounds, including cyclic511, 644 and open-chain645-647 ketones, aliphatic aldehydes,90 benzyl cyanides,93-436 malononitrile,487 rhodanine,144,648 hippuric acid,477 barbituric acid,487 diethyl malonate,487 and malonic acid (Section VI,M). Aliphatic nitro compounds condense smoothly with most benzo[6]-thiophene aldehydes03,141,337,343, 556,640,650 (except 5-hydroxy- and... 

The j8-(3-benzo[6]thienyl)-a-mercaptoacrylic acids (315), prepared by hydrolysis of the corresponding 5-(3-benzo[6]thenylidene)-rhodanine, may be cyclized by iodine in tetrahydrofuran to give the tricyclic compounds (316).648... 

---