Isothiocyanates 4-thiazoline-2-thiones

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). 

In the case of thiazoline-2(3//)-thiones, the mesoionic thiazolo[2,3-h][l,3,4]thiadiazoles are obtained by two different routes (Scheme 65). On the one hand, thione 166 reacts with isothiocyanate via intermediate 167 and with a second equivalent isothiocyanate to afford the mesoionic 168 on the other hand, in the presence of isocyanate, the thione preferentially dimerizes 167 with the open-chain carbodiimide 169 to give the mesoionic 170. Addition of acid with removal of an amine group converts 170 into the symmetric heteroaromatic amine (171) (88CB1495 92T1285). The related transformation of an imidazoline into 1,3,4-thiadiazoles has also been described (90T4353). 

Decomposition of a different type is observed on irradiation of the 3-thiazoline-2-thione (225) resulting in loss of sulfur and the formation of the vinyl isothiocyanate (226)181 further irradiation yields the isoquinoline-1-thione (227). 

Eckinochloa crus galli, 135 Electronic circuits, 438 Electronic transition, calculation of, in 2-methylthiothiazole, 380 in A-4-thiazoline-2-thione, 380, 381 Electrophilic centers, ambident isothiocyanate, 126 and HSAB, 88... 

Abstract The high synthetic versatiUty exhibited by the isothiocyanato motif has allowed its use as a building block in the preparation of a plethora of derivatives. When present in carbohydrates, the strong electrophilicity shown by isothiocyanates, together with the possibility of undergoing cycloaddition reactions has made it possible to access a broad spectrum of heterocyclic compounds, of either synthetic or pharmaceutical interest. Among them, noteworthy are 1,3-oxazolidine- and l,3-oxazinane-2-thiones (cyclic thiocarbamates), 2-amino-2-oxazolines (cyclic isoureas), 2-amino-2-thiazolines (cyclic isothioureas), nucleosides, and spironucleosides. 

Keywords Amino-oxazolines Amino-thiazolines Nucleosides Oxazolidine-2-thiones Sugar isothiocyanates Thiocarbamates... 

Thiazoline-2-thiones from isothiocyanates via dithiourethans—4-Thiazolin-2-ones from isocyanates via thiourethans s. 17, 648 dithiourethans cf. E. Gherbuliez et al., Helv. 48, 1414 (1965)... 

In an extension of this work, analogous [4 + 2] and [4+1] cycloadditions of thiocarbamoyl isothiocyanates (161) have been examined. Their interaction with isocyanides under restrained conditions yields 2-amino-5-imino-2-thiazoline-4-thiones (162) as deeply coloured stable... 

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). 

In a weakly alkaline solution, isothiocyanate reacts with the a-amino group of cysteine (Figure 2.64). The reaction of isothiocyanates with cystine leads to the cleavage of disulfide bond (-S-S-) with the formation of cysteine sulfenic acid and a dithiocarbamic acid ester. Dehydration of this ester yields 5-amino-l,3-thiazine-4-one-3-thione derivative and elimination of hydrogen sulfide produces a cyclic 2-thiazoline-4-carboxylic acid derivative (Figure 2.65). Reaction of cystine with thiocyanates (R-S-C=N), formed by spontaneous isomerisation of isothiocyanates, produces disulfide Cys-S-S-R and -thiocyanoalanine, which cyclises to 2-thiazoline derivative (Figure 2.66). 

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