Synthesis of 2-Aryl Benzothiazoles via K(2)S(2)O(8)-mediated Oxidative Condensation of Benzothiazoles with Aryl Aldehydes

Nontransition metal-catalyzed synthesis of 2-aryl benzothiazoles was achieved through K(2)S(2)O(8)-mediated oxidative condensation of benzothiazoles with aryl aldehydes. The same transformation can also be effected when the aryl aldehydes were replaced with phenylglyoxylic acids.     

Synthesis of oxindoles via visible light photoredox catalysis

2-Electron-withdrawing-group-substituted 2-bromoanilides can be converted to the corresponding 3,3-disubstituted oxindoles with high efficiency under visible light irradiation by using fac-Ir(ppy)(3) as the photoredox catalyst. This protocol is suitable for the synthesis of oxindoles with chloro and bromo atoms attached to the phenyl ring.     

A convenient synthesis of 2-acyl benzothiazoles/thiazoles from benzothiazole/thiazole and N,N'-carbonyldiimidazole activated carboxylic acids

A convenient and efficient strategy for the synthesis of 2-acyl benzothiazoles/thiazoles has been developed. The treatment of benzothiazole/thiazole with allylic Grignard reagents readily generates the corresponding 2-Grignard reagents, which is followed by a reaction with N,N'-carbonyldiimidazole activated carboxylic acids to afford various 2-acyl benzothiazoles/thiazoles products. The synthetic method is applicable to a wide array of carboxylic acids and allows easy access to 2-acyl benzothiazoles/thiazoles with considerable yields under mild reaction conditions.     

Synthesis of 2- and 2,5-substituted benzoxazoles and benzothiazoles

A number of 2- and 2,5-perfluoroalkyl and perfluoroalkylether substituted benzoxazoles and benzothiazoles have been prepared. Their relative hydrolytic stability has been examined. In all cases the benzothiazoles were more stable that the benzoxazoles. Substituents in the 2-position offering steric hindrance improve hydrolytic stability.     

A simple approach to benzothiazoles from 2-chloronitrobenzene,elemental sulfur,and aliphatic amine under solvent-free and catalyst-free conditions

A novel solvent-free and catalyst-free synthesis of benzothiazoles from 2-chloronitrobenzene, elemental sulfur, and aliphatic amine has been developed. The reaction tolerated a wide range of functionalities, and various benzothiazoles were synthesized in moderate to good yields in the absence of external oxidant or reductant.     

Reaction of N,N-dichlorosulfonamides with aryl isothiocyanates

The reaction of aryl isothiocyanates with the N,N-dichloroamides of arenesulfonic acids and with the morpholide of sulfamic acid has been studied. Instead of the expected products of the oxidative imination of the aryl isothiocyanates, 2-(arylsulfonylamino)benzothiazoles and 2-(morpholinosulfonylamino)benzothiazoles, respectively, were obtained.     

Base-catalyzed hydrogen-deuterium exchange in some 5-substituted benzothiazoles and in thiazolo-[4,5-c]pyridine. effect of substituents and polar effects of the aza group

The rates of base-catalyzed hydrogen-deuterium exchange at C-2 in some 5-substituted benzothiazoles and in thiazolo[4,5-c]pyridine were studied. Transmission through the thiazole ring of the effects of substituents in the benzothiazoles and of the polar effects of the aza group in the thiazolopyridine, was assessed from these data.     

Peroxide-mediated oxidative coupling of primary alcohols and disulfides: Synthesis of 2-substituted benzothiazoles

A peroxide-mediated protocol for the synthesis of 2-substituted benzothiazoles was developed, starting from bis(o-aminophenyl) disulfides and primary alcohols. Eleven differently 2-substituted benzothiazoles were prepared in moderate to excellent yields using di-tert-butyl peroxide (DTBP) as an oxidant.     

Heterocyclic Quinones in the Nenitzescu Reaction. Synthesis of Furo- and Pyrrolobenzothiazoles from 2-Methyl-4,7-dioxobenzothiazole

Treatment of the enamines of acetylacetone and benzoylacetone with 2-methyl-4,7-dioxobenzothiazole under Nenitzescu reaction conditions gave furo[2,3-e]benzothiazoles (in acetic acid) and pyrrolo[2,3-e]benzothiazoles (in nitromethane). Using enamines of acetoacetic ester gave exclusively pyrrolo[2,3-e]benzothiazoles.__________Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 252–258, February, 2005.     

A novel reaction between benzothiazoles and diaroylacetylenes in the presence of Meldrum’s acid: ring expansion of benzothiazoles to functionalized 1,4-benzothiazines

A novel and efficient ring expansion of benzothiazoles to functionalized 1,4-benzothiazines is described. The reactive 1:1 zwitterionic intermediates formed by addition of benzothiazoles to diaroylacetylenes were trapped with Meldrum’s acid under mild reaction conditions to produce 2-[2-hydroxy-2-aryl-2H-1,4-benzothiazin-3(4H)-yliden]-1-aryl-1-ethanones in excellent yields.     

Copper-catalyzed solvent-free redox condensation of benzothiazoles with aldehydes or benzylic alcohols

An efficient and practical method for the construction of 2-aryl- and 2-alkyl-substituted benzothiazoles via a copper-catalyzed redox condensation process between benzothiazoles and aldehydes or benzylic alcohols has been developed. The reaction proceeded under mild reaction conditions using environmentally benign tert-butyl hydroperoxide (TBHP) as the oxidant. A reaction mechanism involving the ring-opening of benzothiazoles initiated by the attack of acyl radical on the thiazole ring and intramolecular condensation is proposed based on the isolation of an anilide disulfide intermediate.     

Ru(III)-catalyzed oxidative reaction in ionic liquid: an efficient and practical route to 2-substituted benzothiazoles and their hybrids with pyrimidine nucleoside

An efficient, practical and environmentally benign synthesis of 2-substituted benzothiazoles was developed through RuCl₃-catalyzed oxidative condensation of 2-aminothiophenol with aldehyde in ionic liquid by using air as the oxidant. With this procedure, a series of 2-substituted benzothiazoles and benzothiazole/pyrimidine nucleoside hybrids with antimicrobial activities were efficiently prepared from easily accessible starting materials.     

水相铜催化α-酮酸与邻氨基苯硫酚合成苯并噻唑化合物

发展了一种新颖的水相α-酮酸与邻氨基苯硫酚合成苯并噻唑化合物的方法。在CuCl₂•2H₂O的催化下,通过该反应顺利合成了2-取代苯并噻唑化合物,产率较高,底物适应性较好。      

High resolution mass spectrometry.—II Some substituted benzothiazoles

The mass spectra of nineteen substituted benzothiazoles have been recorded and the identity of the various ions in the mass spectra has been established by high resulution (accurate) mass measurement. Deuterium labelling has been used to elucidate the fragmentation processes of these compounds. The parent compound of the series, benzothiazole, exhibits the loss of hydrogen cyanide and carbon monosulphide from the parent ion as the most important decomposition pathways. The hydrogen atom concerned in the loss of hydrogen cyanide is shown to originate from the 2-position of benzothiazole, while in 2-substituted benzothiazoles, different mechanisms are apparent for the loss of hydrogen cyanide, and these are clarified by deuterium labelling. Some substituted benzothiazoles can lose sulphur from their molecular ions, a process which does not occur in benzothiazole itself. The substituted benzothiazoles undergo many other types of fragmentations, in some cases retaining the substituent, and in other cases losing it prior to collapse of the thiazole ring.     

Methanesulfonic Acid/SiO2 as an Efficient Combination for the Synthesis of 2-Substituted Aromatic and Aliphatic Benzothiazoles from Carboxylic Acids

Methanesulfonic acid/SiO₂ (1 mL/0.3 g) was found to be as an expeditious mixture in the synthesis of 2-substituted aromatic and aliphatic benzothiazoles at 140 °C using carboxylic acids. After a simple workup, benzothiazoles were obtained in good yields. Simplicity, use of widely available and diverse carboxylic acids, and easy handling of the reaction conditions are among the benefits of the method.     

An analysis on the transmission of electron density through sulphur atoms in the quaternization reactions of benzothiazoles

The kinetics of quaternization of a number of 2-substituted benzothiazoles with alkyl iodides and phenacyl bromide have been studied in nitrobenzene. The order of reactivity of different substituted benzothiazoles has been found to be -H > NO₂ > Cl. The relative reactivity of 2-amino and 2-methyl derivatives has been ascribed to a solvation phenomenon. The analysis of rho values from the Hammett equation suggests two possible routes for the transmission of electron density.     

Green and Highly Efficient Synthesis of Mono‐ and Bis‐Benzothiazoles in the Presence of Fe(SD)3 under Ultrasound Irradiation

A convenient, practical, green, and environmentally friendly method was developed for the synthesis of benzothiazoles from 2‐aminothiophenol and various aldehydes. Bis‐benzothiazoles were synthesized in high yield under mild reaction conditions. Products were obtained in the presence of in situ prepared Fe(SD )₃ [iron(III ) dodecyl sulfate] as a combined Lewis acid–surfactant catalyst (LASC ) in water under ultrasound irradiation.     

Synthesis of 2-N-substituted benzothiazoles via domino condensation-hetero cyclization process,mediated by copper oxide nanoparticles under ligand-free conditions

A simple and highly practical method for the synthesis of 2-N-substituted benzothiazoles has been developed by using nanocopper oxide as a recyclable catalyst. The present tandem process allows to get access to a wide range of 2-N-substituted benzothiazoles in good to excellent yields by the reaction of 2-iodo aniline with carbon disulfide and piperidine in presence of KOH as a base and DMSO as a solvent under ligand-free conditions.     

Na2S2O4-Mediated Cyclocondensations of 2,2'-Disulfanediyldianilines with Aldehydes: A Facile and Inexpensive Method for the Synthesis of 2-Substituted Benzothiazoles

A facile and inexpensive method for the synthesis of 2‐substituted benzothiazoles has been developed by Na₂S₂O₄‐mediated cyclocondensations of 2,2′‐disulfanediyldianilines with aldehydes. In the presence of Na₂S₂O₄ and 4 Å molecular sieves, a variety of 2‐substituted benzothiazoles were obtained from the reaction of 2,2′‐disulfanediyldianilines with aldehydes in moderate to high yields.     

水相中苯并噻唑类衍生物的微波辐射合成

在水相中建立了一种简单实用,廉价的2-碘芳胺与芳醛和硫氰酸钾反应生成苯并噻唑衍生物的微波辅助铜催化体系。该体系只需以碘化亚铜和1,10-菲罗啉为催化剂,以碳酸铯为碱的100 ℃水中反应30 min,就能得到大量苯并噻唑衍生物,最高产率达94%。