From A-4-thiazoline-2-one

A-4-Thiazoline-2-ones and ring substituted derivatives are usually prepared by the general ring-closure methods described in Chapter II. Some special methods where the thiazole ring is already formed have been used, however. An original synthesis of 4- 2-carboxyphenyl)-A-4-thiazoline-2-one (18) starting from 2-thiocyanato-2-halophenyl-l-3-indandione (19) has been proposed (Scheme 8) (20, 21). Reaction of bicyclic quaternary salts (20) may provide 3-substituted A-4-thiazoline-2-one derivatives (21) (Scheme 9) (22). Sykes et al. (23) report the formation of A-4-thiazoline-2-ones (24) by treatment ef 2-bromo (22) or 2-dimethylaminothiazole (23) quaternary salts with base (Scheme 10). 

Decomposition of diazonium salts obtained from 2-aminothiazole (4) (29, 34. 35) could be an interesting reaction to introduce O in A-4-thiazoline-2-one. Acidic hydrolvsis of ethers (36. 37). oxidative hydrolysis... 

A-4-Thiazoline-2-one and its derivatives absorb in the region of 247 nm [244 nm in cyclohexane (106)]. Thks band involves a transition (30. 102). From PPP calculations, the first excited state of... 

The formation of trisubstituted A-4 thiazoline-2-ones from the corresponding thiones analogs can be performed by oxidation with hydrogen peroxide under basic conditions. This reaction is strongly dependent on the pH of the medium. Higher yields are obtained in strongly alkaline solution (883). 

Reduction of A-4-thiazoline-2-one by zinc dust gives low yields of the corresponding thiazoles (36, 231). The formation of thiochrome (95) results from an intramolecular nucleophilic attack (Scheme 47) (232). 

Schiff bases, 256-259, 268, 270 to amines. 40 from aminothiazoles, 98 with 2-amino thiazoles, 30, 40 complexes of, 99 cyclization to, 42 IR spectra of, 41 in reduction by AlLiH,. 14 in reduction by NaBH4, 14 LTV spectra of, 41 see also Thiazolylamidines Schistosomacidal, 141 Schistosomiasis japonica, 145 Schotten-Bauman reaction. 51. 123 Sedative, 145. 148,438 Selective herbicide, 135 Self association, effect of, on UV spectra of A-4-thiazoline-2-thione. 381 A-4-thiazoline-2-one, relation with protomery, 377... 

Auto-association of A-4-thiazoline-2-thione and 4-alkyl derivatives has been deduced from infrared spectra of diluted solutions in carbon tetrachloride (58. 77). Results are interpretated (77) in terms of an equilibrium between monomer and cyclic dimer. The association constants are strongly dependent on the electronic and steric effects of the alkyl substituents in the 4- and 5-positions, respectively. This behavior is well shown if one compares the results for the unsubstituted compound (K - 1200 M" ,). 4-methyl-A-4-thiazoline-2-thione K = 2200 M ). and 5-methyl-4-r-butyl-A-4-thiazoline-2-thione K=120 M ) (58). 

Phenyl isothiocyanate and anhydrous K-carbonate in benzene ice-salt-cooled and treated with 2-mercapto-3-pentanone, more benzene added, and heated to reflux N-phenyl-S-(3-oxo-2-pentyl) dithiourethan (Y 87%) refluxed 3 hrs. with anhydrous ZnGl2 in abs. methanol 3-phenyl-4-ethyl-5-methyl-4-thiazo-line-2-thione (Y 90%). F. e., also 4-thiazolin-2-ones from isocyanates via thio-uretbans and without isolation of the intermediates (cf. Synth. Meth. lA, 655), s. K. Riihlmann, A. GrosaJski, and U. Schrapler, J. pr. 11, 54 (1960). 

Phytopathogenic microorganisms, 136 Picrates, of amidines, 99 Pigments, 156-168 Piperidine, 46 Piscaine, 146 pKa. pKb, 18 of acylaminothiazoles, 91 and amino-imino equilibrium, 19 of azothiazoles, 107 correlation with sigma values, 19 of 2-methoxy-4-methylthiazole, 389 of 2-methylthiothiazole, in relation with nucleophilicity, 405 representative values, 20 and substituents effects. 19, 91 of A-2-thiazoline-4-one, from UV experiments, from potentiometry. 423 of A-4-thiazoline-one, 389 of 2-thiazolyl-oxides, 409 Plant growth regulator, 133, 134, 137 Plastics, 170... 

Japanese workers were the first to use the reactive properties of nitrile compounds to synthesize thiazolo[3,2-a]pyridin-3(2//)-ones (77S839). Ethyl a-cyanocinnamate (88, R = Ph, R = CO Et) reacts with ethyl mer-captoacetate in the presence of triethylamine to give 5-amino-2-benzyli-dene-6,8-bis (ethoxycarbonyl )-7-phenyl-7//-thiazolo [3,2-n]pyridin-3(2//)-one (89, R = R- = Ph, R = R = C02Et), which is also obtained from the reaction of 5-benzylidene-2-ethoxycarbonylmethyl-2-thiazolin-4-one (90a) with ehtyl a-cyanocinnamate (77S839). Reaction of 90a,b with ben-zylidenemalononitrile (88, R- = Ph, R" = CN) and of 90c with ethyl a-cyanocinnamate furnish the respective bicyclic compounds 89 [83ZN(B)781] (Scheme 21). Similar results were also obtained from 88 (R = furan-2-yl-or thiophen-2-yl) (86M105). 

Imidazo[2,l-h]thiazoles [C3NS-C3N2]. Further examples of the reaction between 2-amino-thiazoles (or -thiazolines) and a-bromo-ketones to give imi-dazo[2,l-6]thiazoles (126) have been reported this ring system has also been obtained from imidazolidine-2-thione and a-bromo-ketones, or pro-pargyl bromide, and from l-(2-methoxyethyl)-4-phenylimidazolidin-2-one... 

Treatment of 2-imino-3-phenyl-4-amino-(5-amido)-4-thiazoline with isocyanates or isothiocyanates yields the expected product (139) resulting from attack of the exocyclic nitrogen on the electrophilic center (276). Since 139 may be acetylated to thiazolo[4,5-d]pyrimidine-7-ones or 7-thiones (140). this reaction provides a route to condensed he erocycles (Scheme 92). 

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