2- benzthiazole

Benzoxazol-4-fluoro-aniline 77 and benzthiazol-aniline 80 both provided the linear product in very good overall yield. This was considered to be the normal or... 

Methylation of 2- or 4-methylquinazoline is reported to proceed with difficultyj" but 4-methylquinazoline has been quaternized with methyl iodide. The product was very hygroscopic and, although not purified, was shown to consist mostly of 1,4-dimethylquinazolinium iodide, since it gave the same cyanine dye (11) with 2-methylthio-benzthiazole metho-toluene-p-sulfonate as did l-methyl-4-methyl-thioquinazolinium iodide (of unambiguous structure) with 2-methyl-benzthiazole methiodide. ... 

Polarographic techniques have been used by Sturm and Hans to demonstrate that certain amino-thiadiazoles and -benzthiazoles exist in the amino form (cf. also references 62, 63). This method, which involves comparison of the polarographic rdeuction potentials of the potentially tautomeric substance with those of alkylated reference compounds, has not been applied often, but may well prove to be a means to obtain qualitative information quickly. There is a possibility that the method can be modified to yield quantitative data. ... 

The simple methyl compounds do indeed contain methyl groups, e.g., methylthiazoles exist as such and not in the methylene form."" The structures of compounds of the pyrophthalone type containing a benzimidazole and benzthiazole nucleus, e.g. 228, have been discussed. Bis (benzimidazolyl) methanes (229) absorb light in the... 

Nitro-l-thiocyanato-benzol liefert bei der Elektrolyse an Quecksilber-Kathoden (in 0,5 nHCl) bis 88% d. Th. 2-Amino-1,3-benzothiazol-3-oxidl. An Blei-Kathoden wird als Hauptprodukt 2-Amino-l, 3-benzthiazol neben 2-Amino-thiophenol1 2, an Kupfer-Ka-thoden ausschlicBlich 3-Amino-4-thiocyanato-phenol gebildet. 

The benzthiazole (62), an example of a stabilised 1-azabuta-1,3-diene, undergoes Inverse type Diels-Alder reactions with electron-rich dienophiles under extremely mild conditions. 

Thiocyanomethylthio)benzthiazole initially forms 2-thiobenzthiazole, which is transient and then rapidly degrades photochemically to benzothiazole and 2-hydroxybenzo-thiazole (Brownlee et al. 1992). 

Thiazole. Auch Mercaptogruppen konnen von der Methinylierung durch s-Triazin erfaBt werden. Dieser Reaktionstyp laBt sich z.B. mit der Umsetzung des s-Triazins mit o-Aminothiophenol zu Benzthiazol (XLII) belegen (25). 

These methods have been applied mainly to imidazol-, benzimidazol-, thiazol-, and benzthiazol-based car-benes,255,274,275 but there are also examples with triazols and tetrazoles.274 In the following, a few representative examples are presented which illustrate the strategies. The complex with a carbazol ligand shows strong luminescence (Scheme 69).272... 

Einen weiteren Einblick in den Reaktionsmechanismus konnten Clusius und Weisser (51) erhalten. Sie synthetisierten das 2-Amino-benzthiazol aus Phenylhydrazin-[/9-16N] iiber das 1-Phenyl-thiosemi-carbazid und konnten aus den 15N-Analysen das intermediare Auftreten eines Diamins beweisen, wie es der RoBiNSONsche Reaktionsmechanismus fordert. 

Several routes have been reported for the synthesis of aromatic poly(azole)s such as poly(benzimidazole), poly(benzoaxazole), and poly(benzthiazole) melt polycondensation of dicarboxylic acid diphenyl esters with tetramines21 and high-temperature solution polycondensation of dicarboxylic acids or their derivatives with tetramine hydrochlorides in PPA.22 PPA acts as condensing agent and solvent. Ueda etal.23 developed a modified method for the synthesis ofpolyazoles with the use of PPM A. 

The Tg of hexafluoroisopropylidene-unit-containing poly(benzthiazole) is 327°C, which is almost the same as that of hexafluoroisopropylidene-unit-containing poly(benzimidazole). The hexafiuoroisopropylidene-unit-containing poly(benzthiazole) is stable up to 470°C in both air and nitrogen. The thermal stability of the hexafluoroisopropylidene-unit-containing poly(benzimidazole) is almost comparable to that of the hexafluoroisopropylidene-unit-containing poly(benzimidazole). The DT,o is 527°C in air and 537°C in nitrogen. 

Direct copolymerization of sulfonated monomers has been used to synthesize sulfonated poly (benzimidazoles), poly(benzoxazole)s, and poly(benzothia-zole)s. As an example, Kim et al. synthesized poly-(benzthiazole)s from 2,5-diamino-1,4-benzenedithiol dihydrochloride and either 2-sulfoterethphthalic acid sodium salt, 5-sulfoisophthalic acid sodium salt, or 2,4-disulfoisophthalic acid potassium salt in poly-phosphoric acid (PPA), as shown in Figure 34. Similar sulfonated poly(benzimidazole) and sulfonated poly(benzoxazole) ° structures have also been synthesized. A general synthetic scheme for each is shown in Figure 35. The stability of these polymers in aqueous acidic environments appears... 

Figure 34. Synthetic scheme for the direct synthesis of sulfonated poly(benzthiazole)s.

The 9-heteroarylthiomethyl derivative 70 was prepared by a comparable process utilizing silver nitrate to catalyze the reaction between carbazole, formaldehyde, and the benzthiazole thiol. °... 

This product is then treated with acryloyl chloride. The initial step in this case probably involves the acylation of nitrogen on the enamine conjugate addition then completes the formation of the lactam ring (23-5). Treatment of that product with triethyl silane then reduces the ring unsaturation and cleaves the benzylic nitrogen bond on the auxiliary to yield (23-6) as the optically pure tmns isomer. Displacement of bromine with the mercapto benzthiazole (23-7) completes the synthesis of izonsteride (23-8) [25]. 

Fig. 1. UV ectraof bis-[N-ethyl-benzthiazole(2) -phospha-methin-cyanine-tetrafluoro-boratc compared with the aza- and the carbomethine-cyanine...

Allmann and Kawada and Allmann carried out X-ray analysis on bis-fN-ethyl-benzthiazole]-phosphamethin-cyanine perchlorate 6b and bis-[N-ethyl-quinoline]-phosphamethin-cyanine perchlorate 7b. In 6b the two heterocycles lie roughly in the same plane. The C—P—C bond angle is 104,6°. The P-C bond lengths, 1,754 and 1,757 be regarded as identical, proving that the C-P-C bond network is... 

Phosphamethin-cyanines, like methin-cyanines, can be protonated by strong acids, forming colorless dications. These can be converted back to the original phosphamethin-cyanines by careful addition of weak bases such as tert.-butanol. This acid-base reaction is least successful in the case of the weakly basic bis-benzthiazole-phosphamethin-cyanine 6. For bis-quinoline-phosphamethin-cyanine 7 b, we obtained vnth perchloric acid in glacial acetic acid the absorption spectrum of the N-ethyl-quinolinium salt. 

Copper(I) salts sometimes have a dual role in the Stille coupling. In the reaction of 3-methyltio-l,2,4-triazine and 2-tributylstannylthiophene (6.33.), for example, besides facilitating the transmetalation copper(I) is also crucial to activate the methyltio group to undergo oxidative addition46 The established Stille coupling conditions also worked well with other substrates, such as 2-methyltio-pyrimidine or 2-methyltio-benzthiazole.47... 

In contrast, some substituted anilines, e.g. 2-nitroaniline,143 2-chIoro-4-(trifluoromethyI)ani-Iine,143 benzene-1,3-diamine,150 or 4-chlorobenzene-1,3-diamine,150 give only very low yields of product or formed tars under the fluorination conditions. The diazotization followed by in situ fluorodediazoniation of the corresponding diazonium salts have been systematically studied in hydrogen fluoridc/base solutions of different composition to ascertain the most important influences on the reaction.329 Besides numerous examples of substituted anilines, various derivatives of pyridine, pyrimidine, 1.3,5-triazine, and benzthiazole have been included in these investigations (yields 45—99%). 

The compound (m.p. 136°) obtained from W,W -diphenylthiourea is in fact83,84 l-(benzthiazol-2 -yl)-l,2,3-triphenylguanidine (43) as suggested by its infrared and ultraviolet spectra88 and shown by its independent synthesis from 2-anilinobenzthiazole (44) and diphenyl-carbodiimide.64 Its degradation to s-triphenylguanidine and 2-amino-benzthiazole derivatives82 (see also ref. 63) are thus accounted for. 

R = Et) yields, by the familiar Hugershoff cyclization,114 the substituted benzthiazole 128 and not the thiadiazolidine 129. In 1,5-dialkyl-aryl group suitable for benzthiazole formation, oxidation by iodine or bromine causes mainly S-dealkylation and subsequent formation of cyclic disulfides (126)137 in two cases, however, the formation of thiadiazolines (129 R = PhCH2, R = Me, R" = Me or Et and R = CH2=CHCH2, R=p-C6H4Me, R" = Me)137-138 as additional products in undisclosed yields, has been observed. 

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