Benzothiazolium salt

Benzothiazolium Salts. The benzothiazolium A -phenacylide adds to the endocyclic double bond of methylenecyclopropenes that have no acyl group in the 4-position to give stable [3 + 2] cyclo-adducts (217). This is claimed to be the first example of the formation of stable [3+2] cycloadducts in the reaction of 1,3-dipoles with methylenecyclopropenes. Other cycloadditions of benzothiazolium iV-phenacylide with olefinic dipolarophiles from the same team are also mentioned. Various reactions of other benzothiazolium salts have also been described.  

Gruener, R. Maul, and H. Schepp, Helv. Chim. Acta, 1981, 64, 648. 

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

The condensation reaction of some selected furo[3,2-b]pyrrole aldehydes (8g, 266,267) with benzothiazolium salts was carried out in refluxing methanol with pyridine as catalyst giving 269a-d <2004MOL241>. 

Benzothiazolium salts in aqueous solution with tetraethylammonium perchlorate as supporting electrolyte are reduced in two one-electron steps.270 The first produces a radical that dimerizes with a radical-substrate reaction as the rate-determining step. The product is dimerized in the 2-position. Reduction at the potential of the second step produces the 2,3-dihydrobenzo-thiazole. 

Benzothiazolium salts such as (168) have also been claimed to behave as spectral sensitizers (81JAP56078842). 

The C-3 atom of the pyrido[l,2-a]pyrimidine (63 R = H) reacted with iV,iV -diphenylformamidine in acetic anhydride301 and with naphtholactam in phosphoryl chloride.302 Compound 63 (R = 8-Me) reacted at position 3 with various benzothiazolium salts in the presence of bases.109 Under more drastic conditions the 8-methyl group also reacted. 

The reactivity of these methyl groups is normally enhanced by nitrogen atom quaternization. Benzotroponopyridinium salt 505 with two molecules of azulene aldehyde condenses to afford blue-black bis(azulenylvinyl) dye 506 (Amax 536 nm 62ZC369). Furthermore, oxazolium salt 507 condenses with activated benzothiazolium salt 508 (Scheme 134) to form unsymmetri-cal trimethine cyanine 509 (63UP1). (Dyes 512a,b arise from methylthio exchange Section IV,A,5,e.)... 

The condensation of thioether 605 and benzothiazolium salt 511 affords cyanine dye 607. This monomethinecyanine (Amax 553 nm) absorbs at nearly as high a wavelength as the symmetrical thiafranethinecyanine (cf. 94KGS193). 

Strong acids react nearly quantitatively with DTDAFs of type 47 under reformation of their starting material, the A -a I kyI benzothiazolium salts (64BSF2857). Using the violet-colored derivative 130, this protonation became visible (81HCA648) (Scheme 52). 

An analogous reaction had already been observed for the benzothiazolium salts of the dicarbocyanine dye series, with the difference that the dimerization was reversible and an equilibrium was established with the monomers in acetonitrile solution100 (Scheme 73). 

Ring expansion of iu-bromoalkyl benzothiazolium salt into A-formyl derivative of benzo[A][l,4]thiazonine has been reported <1995JOC2597>. 

Aza-enediynes are a new class of anti-neoplastic agents that produce a cytotoxic effect through an aza-Bergman cyclization (1) of an enediyne core to a 1,4-didehydrobenzene reaction intermediate. Both Bergman and benzothiazolium salt diradical cyclizations are illustrated in Eq. 1 and Eq. 2, respectively. 

Instead, only two reaction pathways are used to generate transition metal NHC complexes with thiazol-2-ylidene orbenzothiazol-2-ylidene (i) thermal cleavage of an electron-rich olefin in the presence of a suitable transition metal (see Figure 6.12) [40,41] and (ii) deprotonation of a thiazolium or benzothiazolium salt in the presence of a transition metal (see Figure 6.13) [40,42-44]. 

Benzothiazoles are rather more prone to reductive decyclization than are thiazoles, although it is possible to form benzothiazolines (224) through the sodium borohydride reduction of benzothiazolium salts (223). On hydrolysis these products yield 2-aminothiophenols (225). Prolonged exposure of benzothiazolines to excess sodium borohydride also causes ring opening to aminothiophenols, as does reaction with LAH. In this last case the substrates for reduction may be benzothiazoles (226), which presumably initially form benzothiazolines with the reagent (Scheme 18). ... 

The quaternary salts of A -heterocycles are readily reduced and often give reversible one-electron reduction waves, as, for example, with pyridium salts [122]. Dimers have been obtained by this pathway e.g. from acridizinium and benzothiazolium salts [116]. Such processes are particularly important both with biological substrates (e.g. NAD is reported to give essentially 4,4 -dimers on reduction) [123] and in the monoelectronic reduction of di-cations such as dipyridinium and a variety of diaza polycyclic aromatic di-cations [124]. 

Thiazole gives a transient radical in aqueous solution upon pulse radiolysis. The radical formed under neutral conditions is the 3-hydrothiazolyl radical (201) for which electronic absorption spectra, acid-base characteristics, and second-order decay kinetics were measured. A derivative of this, the radical from thiamine (vitamin Bj) (202) was also characterized. A role is implied for related radicals (e.g., 203) during the electrochemical dimerization reported for benzothiazolium salts. ... 

The use of thiazolium salts enables the benzoin condensation to proceed at room temperature. It can also be performed in dipolar aptotic solvents or under phase transfer conditions. Thiazolium salts such as vitamin Bi, thiazolium salts attached to y-cyclodextrin, macrobicyclic thiazolium salts, thiazolium carboxylate, ° naphtho[2,l-d]thiazolium and benzothiazolium salts catalyze the benzoin condensation and quaternary salts of 1-methylbenzimidazole and 4-(4-chlorophenyl)-4//-1,2,4-triazole are reported to have similar catalytic activity. Alkylation of 2-hydroxyethyl-4-methyl-l,3-thiazole with benzyl chloride, methyl iodide, ethyl bromide and 2-ethoxyethyl bromide yields useful salts for catalyzing 1,4-addition of aldehydes to activated double bonds. Insoluble polymer-supported thiazolium salts are catalysts for the benzoin condensation and for Michael addition of aldehydes. Electron rich al-kenes such as bis(l,3-dialkylimidazolidin-2-ylidenes) bearing primary alkyl substituents at the nitrogen atoms or bis(thiazolin-2-ylidene) bearing benzyl groups at the nitrogen atoms are examples of a new class of catalyst for the conversion of ArCHO into ArCHOHCOAr. 

Hatrik, S. and Zahradnik, P. (1996). Neural Network Approach to the Prediction of the Toxicity of Benzothiazolium Salts from Molecular StTucture.J.Chem.Inf.Comput.Sci.,36,992-995. 

Halo-pyridinium or -benzothiazolium salts have been applied in the preparation of S-alkyl or S-aryl carbothioates from carboxylic acids via acyloxypyridinium salts (c/. equation 7). 

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