Benzothiazole derivatives

The first empirical and qualitative approach to the electronic structure of thiazole appeared in 1931 in a paper entitled Aspects of the chemistry of the thiazole group (115). In this historical review. Hunter showed the technical importance of the group, especially of the benzothiazole derivatives, and correlated the observed reactivity with the mobility of the electronic system. In 1943, Jensen et al. (116) explained the low value observed for the dipole moment of thiazole (1.64D in benzene) by the small contribution of the polar-limiting structures and thus by an essentially dienic character of the v system of thiazole. The first theoretical calculation of the electronic structure of thiazole. benzothiazole, and their methyl derivatives was performed by Pullman and Metzger using the Huckel method (5, 6, 8). 

Intramolecular cyclization of benzothiazole derivative 698 by a Claisen self-condensation afforded 699 (81JHC1273) (Scheme 120). 

General Procedures for the Reaction of 2-Allyloxy- (or 2-Allylthio)benzothiazole Derivatives with Organocop-per Reagents42 ... 

Salmona et al. [66] used El and CIMS to identify benzothiazole derivatives leached into injections by rubber plunger seals from disposable syringes. One of the compounds was used as a rubber vulcanisation accelerator, and four others were formed during syringe sterilisation with ethylene oxide. Applications of hyphenated chemical impact mass-spectrometric techniques are described elsewhere GC-MS (Section 7.3.1.2), for polar and nonpolar volatile organics, SFC-MS (Section 13.2.2) and TLC-MS (Section 7.3.5.4). 

The bioluminescence of the American firefly (Photinus pyralis) is certainly the best-known bioluminescent reaction, thanks to the work of Me Elroy and coworkers and E. H. White and his group (for references see P, p. 138, 6,168,169)) The substrate of this enzyme-catalyzed chemiluminescent oxidation is the benzothiazole derivative 107 (Photinus luciferin) which yields the ketone 109 in a decarboxylation reaction. The concept of a concerted cleavage of a dioxetane derivative has been applied to this reaction 170> (see Section II. C.). Recent experiments with 18C>2 have challenged this concept, as no 180-containing carbon dioxide was detected from the oxidation of 107 171>. 

Because of its importance in biological areas, special efforts have been made with the synthesis of the thiazolo[2,3-t]-[l,2,4]thiadiazole derivative 308 <2001BML1805>. The pathway started from the benzothiazole derivative 305 which was treated with chlorosulfonylacetyl chloride to form an intermediate 306, which underwent cyclization to a second intermediate 307 with hydrogen chloride elimination. The last step is the attack of the first intermediate 306 at the thiadiazine carbon atom to form the final product 308. 

The first examples were benzene disulfonimide derivatives prepared from o-benzenebis(sulfonyl chloride) or -disulfinic acid with amines or HNO2 respectively <84CHEC-I(6)914>, or benzothiazole derivatives (94) obtained from benzenesulfonamides or azides containing ortho SR or SOR groups... 

When strongly heated, diaryl-5-imino-l,2,4-dithiazole-3-one (34 X = O, R = R = 4-MeOC6H4) loses COS to give a benzothiazole derivative (89) (91JPR579>. 3-Imino-l,2,4-oxathiazilidine-3-one (90) decomposes in solution at room temperature to give a carbodiimide (91) (Equation (6)) <86CB3737>. 

Addition reactions of several thiazole and benzothiazole derivatives to DMAD have been reported. Thiazole (383a), for example, gives a 1 2 adduct (384a) on treatment with DMAD, whereas in the reaction of 2-ethylthiazole (383b), a S,6-dihydrothiazolo[3,2-a]azepine (385) is... 

In the middle of the 1950s, Knott reported the synthesis of dyesmffs based on benzothiazole derivatives. Alkylation of Al-methylbenzo-l,3-thiazole-2-thione with a-bromoacetophenone and deprotonation of the resulting thiocarbonylium salt 5 yielded, after spontaneous desulfurization of the intermediate thiirane (7), the alkylidene derivative 8 (18) (Scheme 5.1). In order to rationalize the reaction, thiocarbonyl ylide 6 was proposed as the precursor of thiirane 7. To the best of our... 

In similar studies, the reduction potentials of 1,2-benzothiazole derivatives in DMF were correlated to antimycotic activity [166], and those of 1,3,5,7-substituted-1,3-dihydro-2H-l, 4-benzodiazepin-2-ones and benzodiazepine-2-thiones in dimethylformamide (DMF)-water solutions were correlated to inhibition of orientation reactions and to protection from electric shock [167]. 

Benzothiazole derivatives with good leaving groups at the 2-position of the heterocycle can also be used as reactive anchors. An example with chlorine as the leaving group is 11 ... 

Alkyl-A2-l,2,3,4-thiatriazolines 52 decompose on heating above 90 °C to form benzothiazole derivatives 53 <1971AP687, 1977JOC1159>. The (2 -cyanomethyl) derivative 10 (R = CH2CN) decomposes at 90°C to the 2-(methylamino)benzothiazole derivative 52 rather than to the fused 1,2,4-thiadiazolimine 54 that would have been expected as the result from an intramolecular masked 1,3-dipolar (see Section 6.09.6.2) cycloaddition (Scheme 11) <1992J(P1)181>. 

Reduction of dinitrobenzothiadiazoles 280 with iron dust in acetic acid gave diamines 281 (Scheme 39). The reaction of diamines 281 with selenium dioxide gave [l,2,5]selenadiazo[4,5-c]-2,l,3-benzothiazole derivatives containing a hypervalent sulfur atom 82 and 83 in 40% and 82% yields, respectively <1997T10169>. 

An efficient combinatorial solid-phase synthesis of asymmetric cyanine dyes was developed by Isacsson and Westman [17] using a Rink amide polystyrene resin. The picolinium and lepidinium salts 6 were linked to the solid-phase resin by amide coupling, then the benzothiazole derivatives 7 were subsequently condensed with the coupled picoline and lepidine moieties to give the yellow to blue (Amax ahs = 420-590 nm) asymmetric, fluorescent (Amax em = 480-650 nm) cyanine dyes 8 (Scheme 5.2, Fig. 5.3). As a consequence of restricted rotation upon intercalation, the fluorescence quantum yields increase significantly when these dyes are bound to DNA. 

The organotin cyanometallates were also used to intercalate a range of organic compounds such as thiazole and benzothiazole derivatives, polyaniline or... 

Similarly, the N-cumyl benzene sulfonamide 7 (Scheme 5) undergoes metalation-diverse electrophile quench reactions its quenching with DMF leads to 8, which, after OTMS protection, may be further metalated and quenched with iodine to give 10 the latter is transformed under mild conditions into new benzothiazole derivatives 11 and 12 [12]. 

Benzotriazole-mediated reactions feature in synthetic routes to the isoindolo- and pyrrolo-fused benzothiazole derivatives 272 (e.g. R1 = CH3, R2 = R3 = H) and 273 (e.g. R1 = R3 = H, R2 = Cl) in good overall yields the common precursors were the thioamines 271... 

The reactivity of i satin derivatives towards o/T/io-aminophenol and ortho-aminothiophenol has been the subject of a number of reports and some of the products obtained are quite intriguing. The first report attests that 1-acetylisatin reacts with o-aminophenol to furnish a ring opened product in ethanol as well as in AcOH. The same result occurred with o-aminothiophenol in acetic acid, whilst in ethanol two different products were formed in a disproportionation reaction, as can be inferred from the change of the oxidation state of what was the 1-acetyli satin C-3 ketone group. The structures were assigned based upon spectroscopic data and, for the benzothiazole derivative, on comparison with a sample... 

---