Benzothiazoline thione

Di(2-ethylhexyl) amino methyl) benzotriazole Benzothiazoline thione derivatives Benzotriazole... 

Benzothiazoline thione Substituted dimercapto-thiadiazole Imidazolidine dimethylene bis phosphoro dithioate Derivatives of pyridine, pyrazine, pyrimidine and pyridazine and their fused ring derivatives Triaryl phosphates Triphenyl phosphate Tritolyl phosphate... 

Benzothiazoline, N-methyl-2-methylene-structure, 6, 238 Benzothiazolines aromatization, 6, 270 oxidation, 6, 272 structure, 6, 238 synthesis, 6, 323, 325 Benzothiazoline-2-thione, 3-methyl-in organic synthesis, 6, 329 Benzothiazoline-2(3 f/)-thiones tautomerism, 6, 248 Benzothiazolin-2-one alkylation, 6, 286 Benzothiazolin-2-one, 3-methyl-hydrazone... 

Alkylation of 2-thiopyridone and of 2-thiobenzoxazolone has been described by Dou et al.195 Yields are good, and only S-alkylation is detected. In a later study, A4-thiazoline-2-thione, thiazolidine-2-thione (130) and benzothiazoline-2-thione have been alkylated, using the phase transfer technique.196... 

If o-hydroxy azo compounds (LXXVII) are used instead of o-amino phenols, then, under pressure at 200° C benzoxazoline-2-thiones (LXXVI) are formed along with 2-(phenylamino) benzoxazoles (LXXVIII (193) (see Table 12, method B). Azobenzene on the other hand yields only benzothiazoline-2-thione. 

Benzothiazoline-2-thiones (CI 11) and their derivatives can be prepared from o-amino thiophenols and carbon disulfide (method A) 166,221,282). On the industrial scale, these compounds, which are important vulcanization accelerators, are prepared from anilines, sulfur and carbon disulfide under pressure and at high temperature (200° C) (method B). In spite of many attempts, the mechanism of this reaction has not been established. Sebrell and Boord 211 mention the following plausible mechanisms ... 

According to Kimijima and Miyama [215, 216], the reaction of aniline with sulfur and carbon disulfide yields the precursor 2-(phenyl-imino) benzothiazoline (CIV) at low temperature and short reaction times. Further reaction of (CIV) with carbon disulfide then yields the benzothiazoUne-2-thione derivatives as mentioned in Section 111.1. 

In an I.G. Farben patent [180] the use of disulfur dichloride is described in place of sulfur (method BJ. Possibly the intermediates here are 1,3,2-benzothiazathiolium chlorides (CV) which react with carbon disulfide to give benzothiazoline-2-thiones (CIII). In some instances, the cycUzations are carried out in the presence of sodium hydrosulfite or sodium sulfide. A peculiarity of this reaction is that, simultaneously with the cyclization, chlorination of the arylene ring occurs. Thi.s is not a general rule though. It happens with aniline, o-toluidine, o-anisidine and oc-naphthylamine but not with /)-phenetidine, )S-naphthylamine or benzidine. It seems quite clear therefore that the para position of the aniline must be free if chlorination is to take place, since it is in this position that the chlorine atom is brought in. With anthranilic acid there is formed 4-carbox -6-phenylaminobenzothiazoline-2-thione which shows that the chlorine atom, which is substituted during the reaction, is replaced by a second molecule of anthranilic acid and that decarboxylation occurs at the same time. 

According to Teppema and Sebrell [357], the preparation of benzo-thiazoline-2-thiones from aryl amines, sulfur and carbon disulfide is not generally applicable. This has been confirmed by several other authors. Another synthesis, method C, has been worked out starting with o-nitro chloro benzenes. On warming these products in a solution of sodium hydrogen sulfide with slow addition of hydrogen sulfide in the presence of carbon disulfide, near 90% yields of benzothiazoline-2-thiones are obtained. 

Dunbrook and Zimmermann 113) report still higher yields, even with short reaction times, when sodium polysulfide and carbon disulfide are used (method C ). The essential appears to be the replacement of the chlorine atom by a mercapto group and the reduction of the nitro group to an amino group, followed by ring closure of the resulting o-aminothiophenol with carbon disulfide to the benzothiazoline-2-thione (method A). 

The preparation of benzothiazoline-2-thiones from o-halo or w-halo anilines and carbon disulfide in basic medium is discussed at greater lenght in Section IV.4. 

The various benzothiazoline-2-thiones, which can be synthesized by the methods outlined above, are brought together in Table 15-... 

In this connection it is perhaps worthwhile to reconsider the synthesis of benzothiazoline-2-thiones. These substances can, as already mentioned, be made from o-nitrochlorobenzene with sodium hydrogen sulfide and carbon disulfide (method C). Starting from 0- or w-halo anilines, benzothiazoline-2-thiones are also obtainable with carbon disulfide in strong alkali (55). The intermediate in this reaction is an aryne (CXXXIII). 

Physical Properties of Benzothiazoles. - The electronic spectra of some benzothiazole derivatives have been measured.The luminescence spectra of some benzothiazole derivatives and of the benzothiazoline-2-thiones were also described. The new picosecond laser photolysis system has also been used and gives well-resolved absorption spectra. The and... 

Benzothiazolines and Benzothiazolin-2-ones (and -thiones). The syntheses of substituted spiro-2-benzothiazolines and 2-methoxy carbonyl-2-... 

Michael reaction. 2-Mercaptobenzothiazole undergoes the Michael addition with activated unsaturated compounds such as methyl vinyl ketone, 2- (or 4-) vinylpyridine, divinyl sulphone, and 2-nitrobut-l-ene yielding N-substituted benzothiazoline-2-thiones [e.g. (70) or (71)]. The... 

Amino-l,2-dithiolium salts (8 R = aryl, R = aryl or arylalkyl, R = H or Me) undergo thermal rearrangement to give the corresponding vinylogous benzothiazoline-2-thiones [==CHC(S)R in the 2-position]. ... 

Alkylation Reactions.—The mechanism proposed for the conversion of benzo-thiazoline-2-thione (29 R = CH2CH2OH, X = S) into the corresponding benzothiazolin-2-one (29 X = O) with ethylene oxide in acetic acid is considered to involve ring-opening by the thione sulphur atom to give the j8-sub-stituted ethanol. This reacts with acetate ion or acetic acid at the 2-position to give an acetate, which decomposes to MeC(0)SCHaCH20H and (29 X = O). In support of the mechanism, no desulphurization occurred when the reaction was attempted in acetone or methanol. 

Irradiation of benzothiazoline-2-thiones (34) and acrylonitrile affords 2-alkyhdenethiazoles (35) (Scheme 6). On the other hand, two products (36,37) are formed by the photoaddition of (34) with 1,1-disubstituted alkenes such as methacrylonitrile and methyl methacrylate. Aminothietanes (38) is proposed as intermediates in these photoreactions. Thioformaldehyde formed by the decomposition of the intermediate has been detected by its trapping by a diene. Photocycloaddition reaction of N-unsubstituted... 

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