Benzothiazolination

Scheme 97). Stepanov has thoroughly studied this nucleophilic reactivity some examples are given in Refs. 423 and 424. The formation of 5-benzylidene derivatives involves the same nucleophilic reactivity (422). 5-Benzothiazoline and 5-benzose enazoline derivatives of 2-diphenylaminothiazoline-4-one, have been obtained by nucleophilic addition of the thiazolone on the corresponding benzothiazolium or ben-zoselenazolium salts (433). 

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... 

Benzothiazolin-3-ylacetic acid, 4-chloro-2-oxo-as herbicide, 6, 328 as plant growth regulator, 1, 191 Benzothiazolium bromide, 2-methyl-3-propargyl-nucleating agent... 

However, it has recently been shown (42) that monomeric enamines such as 42 react normally to give the benzothiazoline salt (43) on alkylation with alkyl and benzyl halides. 

Ring-opening is not a mandatory direction of the complexation reaction. Thus, the ring-closed form of the benzothiazoline 395 ligand was found to be preserved in its complex 396 with BuSnCla, whose structure was determined with X-rays (Scheme 146) [93JOM(454)67]. 

The asymmetrical anhydrobase (20) constitutes the first step of the formation of trimethine thiazolocyanine when a 2-methylthiazolium salt reacts either with a benzothiazolium or its opened form [which is bis-o-(formylmethylamino)(diphenyl disulfide] (Scheme 26). In a second step, 20 is protonated by a second molecule of 2-methylthiazolium. It results in cleavage of the benzothiazoline ring, which gives 21 together with the formation of the monomeric anhydrobase (22). Cleavage of the C-S bond of 20 can be explained by the important electronic desaturation of the C atom observed in NMR spectrum and the great polarizability of the C-S bond in this type of ring (48). 

Benzothiazoline, cleavage of ring, 42 polarizabilite of CS bond, 42 Benzothiazolium salts, action on anhydro-base, 43... 

Over the years, many spiropyran structures have been prepared. The pyran component consists of benzopyran or naphthopyran and the heterocyclic part consists of indoline, benzothiazoline, benzoxazoline, benzoselen-azoline, phenanthridine, acridine, quinoline, benzopyran, naphthopyran, xanthene, benzodithiole, benzoxathiole, and saturated heterocyclic rings such as pyrolidine and thiazolidine. 

Absorption maxima for a wide range of heterocyclic systems are shown in Figure 1.5.2 When the indolyl residue 8a is replaced by other heterocyclic residue, a somewhat small shift in the Xmax occurs. Replacement with a benzothiazoline residue, 8c, results in a bathochromic shift. Comparison between saturated heterocycles 8d-8f and the corresponding benzoderiv-atives 8a-8c shows that the conjugation produced by the benzene nuclei causes a bathochromic shift (ca. 20-50 nm). Replacement of saturated five-membered heterocycles by saturated six-membered heterocycles results in a hypsochromic shift. In the case of the piperidine series (8g) a significant hypsochromic shift occurs, due to steric hindrance in the colored form. 

The substituent effect in the phenyl group at the 3-position is also observed in the benzothiazoline series.2,17 The thermal fading rate increases with the bulky group at the 3-position, but the colored forms of 3-methoxy and 3-phenoxy derivatives are largely stabilized by an intramolecular interaction with 5-hydrogen atom.2... 

Compounds containing a benzodioxole moiety are oxidized by CYPs to generate a carbene that forms a tightly bound complex with the heme iron, easily measurable by UV-Vis spectroscopy. There are numerous examples in the literature paroxetine, MDP alkylamines, MDP benzothiazines, MDP benzothiazolines and MDP piperazines (see Scheme 11.2) [54—60],... 

In the presence of various metal ions, 2-(fluoroenone)benzothiazoline has been found to rearrange to A-2-mercaptophenylenimine, while a free radical mechanism involving the homolysis of C-S and C-N bonds has been invoked to explain the formation of 3-phenyl-1,2,4-triazole derivatives from the thermal fragmentation and rearrangement of 2-(arylidenehydrazino)-4-(5//)-thiazolone derivatives. The cycloadducts (36) formed from the reaction of 3-diethylamino-4-(4-methoxyphenyl)-5-vinyl-isothiazole 1,1-dioxide (34) with nitric oxides or miinchnones (35) have been found to undergo pyrolytic transformation into a, jS-unsaturated nitriles (38) by way of pyrrole-isothiazoline 1,1-dioxide intermediates (37). 

Reactions of carbonyl compounds such as pyridine 2-carboxaldehyde, glyoxal, biacetyl, or benzil with 2-aminothiophenol on an Fe + template give benzothiazolinate (198) complexes. The complex from pyridine 2-carboxaldehyde, for example, was formulated, on the basis of NMR and Mossbauer spectroscopy and of analysis (C, H, N, and Fe) as the bis-(A,iS)-ligand-bis-aqua complexes of (199), an isomeric form in equilibrium with (198). However as they are diamagnetic it seems more likely that they are [Fe(199)2] 2H20, containing terdentate (N,N,S) (199), than the proposed [Fe(199)2(H20)2]. 

The total antioxidant activity of teas and tea polyphenols in aqueous phase oxidation reactions has been determined using an assay based on oxidation of 2,2,-azinobis-(3-ethyl benzothiazoline-sulfonate) (ABTS) by peroxyl radicals (114—117). Black and green tea extracts (2500 ppm) were found to be 8—12 times more effective antioxidants than a 1-mM solution of the water-soluble form of vitamin E, Trolox. The most potent antioxidants of the tea flavonoids were found to be epicatechin gallate and epigallocatechin gallate. A 1-mM solution of these flavanols were found respectively to be 4.9 and 4.8 times more potent than a 1-mM solution of Trolox in scavenging an ABT 5r+ radical cation. 

Substrate products can be classified as either soluble or precipitating. Soluble peroxidase substrates include o-phenylenediamine, which is converted into a yellow product 2,2 -azino-(3-ethyl)-benzothiazoline-sulfonic acid, which is converted into a green product and tetramethylbenzidine, which is converted into a blue product. Precipitating substrates for peroxidase include 4-chloronaphthol, which yields a blue precipitate and aminoethylcarbizole, which forms a red precipitate. Alkaline phosphatase is most frequently used with p-nitrophenyl phosphate to give a yellow-orange soluble product, or with 5-bromo-4-chloro-3-indo-lyl-phosphate p-toluidine salt to yield an insoluble blue product. 

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... 

The thermolysis of 2,1-benzothiazoline 2,2-dioxides generates aza-o-xylenes which are trapped in situ with maleic acid derivatives to give ris-l,2,3,4-tetrahydroquinoline-2,3-dicarboxylic acid products (Scheme 73) (91SL571) (cf 364). 

The condensation of o-aminobenzenethiol with pyridine-2,6-dicarbaldehyde does not form the corresponding Schiff base but a polyheterocyclic compound which behaves as a tridentate ligand towards nickel(II).2365 In contrast the reaction of 2-(2-pyridyl)benzothiazoline with nickel(II) results in the opening of the heterocyclic ring and in the formation of a Schiff base ligand which coordinates to nickel(II) as a mononegative tridentate ligand.2366,2367... 

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