Isomerization in the Oxidative Cyclocondensation of 2-Aroylmethyl-1H-benzimidazoles with o-Aminothiophenol

Oxidative cyclocondensation of 2-aroylmethyl-1H-benzimidazoles with o-aminothiophenol gave the previously unknown 3-aryl-2-(2-benzimidazolyl)-4H-1,4-benzothiazines and (or) the isomeric 2H-1,4-benzothiazines. 2-(4-Nitrophenacyl)-1H-benzimidazole and 2-phenacylbenzothiazole gave 4H-1,4-benzothiazines which are not liable to isomerize but the reaction of the first compound is complicated by a hydrolytic fission which yields 2-[2-(4-nitrobenzoylamino)phenylthiomethyl]benzimidazole. A mixture of dimethylsulfoxide, acetic acid, and water was used as oxidant and solvent. The effect of the substituent and of the solvent on the tendency of the products to undergo prototropic isomerization in the benzothiazine ring have been studied.     

A New Synthetic Approach Towards the Synthesis of 2-(3-Aryl-2H-1,4-benzthiazin-2-yl)-3-aryl-2H-1,4-benzothiazines

Synthesis of 2-(3-Aryl-2H-1,4-benzthiazin-2-yl)-3-aryl-2H-1,4-benzothiazines (3 a-e) from 3-aryl-5(4H)-isoxazolones (1 a-e) and 2-aminothiophenol (2).     

Bioglycerol-Based Sulfonic Acid-Functionalized Carbon Catalyst as an Efficient and Reusable Catalyst for One-Pot Synthesis of 3- Substituted-2H-1,4-Benzothiazines

Abstract

A simple and efficient synthetic protocol has been developed for the synthesis of 3-substituted-2H-1,4-benzothiazines by using bioglycerol-based sulfonic acid-functionalized carbon catalyst, devoid of corrosive acidic and basic reagents. The developed method has the advantages of good to excellent yields, short reaction times, operational simplicity, and a recyclable catalyst.     

Synthesis and antimicrobial activity of structurally flexible heterocycles with the 1,4-thiazine heterosystem

In this work, 4H-1,4-benzothiazines were synthesized by an efficient synthetic method in a single step involving heterocyclization of substituted 2-aminobenzenethiols with β-ketoester. The structures of the synthesized compounds were confirmed by their analytical and spectral data. The synthesized compounds were evaluated for their antimicrobial activity against bacterial species; E. coli and Bacillus cereus. The synthesized compounds showed significant activity against microorganisms, which can be correlated with the privileged heterocyclic structural scaffolds.     

Synthetic Methodology,Spectral Elucidation,and Antioxidative Properties of Benzothianes and Their Sulfones

This article reflects the synthetic strategies and spectral investigation of 4H-1,4-benzothiazines. 4H-1,4-benzothiazines have been prepared by the condensation and oxidative cyclization of substituted 2-aminobenzenethiol with β-diketones/β-ketoesters in dimethyl sulfoxide and with the oxidation of 4H-1,4-benzothiazines by 30% hydrogen peroxide in glacial acetic acid, which results in the formation of 4H-1,4-benzothiazine sulfones. The compounds were evaluated for their antioxidative properties through in vitro and in vivo studies in Swiss albino mice. The structural assignments of compounds were made on the basis of spectroscopic data and elemental analysis.     

Stereoselective synthesis of 2-alkylidene-3,4-dihydro-3-oxo-2h-1,4-benzothiazines

Metallation of 4-methyl-3,4-dihydro-3-oxo--2H-1,4-benzothiazine with LDA and subsequent reaction with aldehydes leads to diastereomeric aldols 4 and 5. Acetylation followed by acetic acid elimination of the aldols provides a stereoselective and high yield route to 2-alkylidene-3,4-dihydro-3-oxo-2H-1,4-benzothiazines.     

Efficient and Convenient Synthesis of 1,4-Benzoxazines, 1,4-Benzothiazines,Spiro-1,4-benzoxazines,and Spiro-1,4-benzothiazines

An efficient, convenient synthesis of 1,4-benzoxazines, 1,4-benzothiazines, spiro-1,4-benzoxazines, and spiro-1,4-benzothiazines derivatives was accomplished in good yields via the novel intramolecular cyclization mediated by mild base K₂CO₃ in ethanol solvent. A variety of substrates can participate in the process with good yields, making this methodology have broad applicability. All the structures of synthesized compound have been confirmed by spectral analysis.

Supplemental materials are available for this article. Go to the publisher's online edition of Synthetic Communications ^® to view the free supplemental file.     

REACTION BETWEEN 2,2′-DITHIODIANILINE AND ETHYL 2-OXO-1-CYCLOALKANECARBOXYLATES

Abstract

A study has been carried out on the acid-catalysed reaction between 2,2′-dithiodianiline (1) and ethyl 2-oxo-1-cycloalkanecarboxylates (2a–d). While the 1,4-benzothiazines 3a, b and benzothiazoles 6a, b are obtained from the keto esters 2a, b, mixtures of the 1,4-benzothiazines 3c, d and 4c, d and benzothiazolines 5c, d are obtained from the keto esters 2c, d.

The formation of the benzothiazines 4 falls within the general pattern previously proposed for reactions between 2,2′-dithiodi(aryl- or alkylamines) and ketones.

The benzothiazines 3 arise from an acid-catalysed rearrangement of the benzothiazines 4, involving a [1, 3] sulfur migration.     

SYNTHESIS AND THERMAL REARRANGEMENT OF 2-ALKOXYCARBONYL-3-ALKYL-4H-BENZO[b][1,4]THIAZINES

Abstract

The title compounds (4b-d) together with the benzothiazolines (5b-d) have been obtained by a reaction between 2,2′-dithiodianiline (1) and β-keto esters (2b-d). The reaction between 1 and the β-keto ester 2a gives 1,4-benzothiazine 3a in addition to the benzothiazoline 5a.

It has been established that the 1,4-benzothaizines 4b-d undergo an acid-catalysed thermal rearrangement involving a [1,3] shift of the sulfur atom, giving rise to the isomeric 1,4-benzothiazines 3b-d.     

SYNTHESIS OF SULFONES OF 4H-1,4-BENZOTHIAZINES AND PHENOTHIAZINES

Conversion of 5/7-chloro-4H-1,4-benzothiazines and 1/3-chlorophenothiazines into sulfones is reported. The 5/7-chloro-4H-1,4-benzothiazines were synthesized by the condensation and oxidative cyclization of 2-amino 3/5-chlorobenzenethiol with β diketones in DMSO. The phenothiazines have been synthesized via Smiles rearrangement by the reaction of 2-amino-3/5-chlorobenzenethiol with halonitrobenzenes. 4H-1,4-Benzothiazine and phenothiazine sulfones have been prepared by the oxidation of benzothiazines and phenothiazines with 30% hydrogen peroxide in glacial acetic acid. The structure of all the synthesized compounds has been confirmed by IR and NMR spectral studies.     

Preparation and Some Reactions of 1H-1,4-Benzothiazine Ylides (= 1H-1,4-Benzothioniaazin-4-ide)

A series of fifteen 1H-1,4-benzothiazine ylides were obtained by alkylation of the corresponding 4H-1,4-benzothiazines 1 . Ylides of type 2g–r showed slight [1,2] rearrangements upon thermolysis besides main dealkylation to 1 and olefin production. The ylides of this type underwent redox reactions when treated with hydrazine hydrate alone, giving 3,4-dihydro-2H-1,4-benzothiazines mainly, while ylides of type 2a–f failed to react.     

AN EFFICIENT SYNTHESIS OF 3,4-DIHYDRO-1H-2,3-BENZOTHIAZINE 2,2-DIOXIDES USING AMBERLYST 15 AND AMBERLYST XN 1010

ABSTRACT

Resins Amberlyst 15 and Amberlyst XN 1010 are used in the synthesis of 3,4-dihydro-1H-2,3-benzothiazines 2,2-dioxide. Advantages of this new procedure are simple work-up, high yield and selectivity, easy recovery of the catalyst and no waste problems.     

Efficient and convenient synthesis,characterization, and antimicrobial evaluation of some new tetracyclic 1,4-benzothiazines

In the present study, 20 new tetracyclic 1,4-benzothiazines (4a–4 t) were conveniently synthesized in good yields and characterized by different spectral and physical techniques. The in vitro antimicrobial evaluation of the synthesized benzothiazine derivatives was performed by serial dilution against two Gram-positive bacteria [Bacillus subtilis (MTCC 441) and Staphylococcus epidermidis (MTCC 6880)], two Gram-negative bacteria [Escherichia coli (MTCC 1652) and Pseudomonas aeruginosa (MTCC 424)], and two fungal strains [Candida albicans (MTCC 227) and Aspergillus niger (MTCC 8189)]. The derivatives 4 l and 4 t were found to be more potent than standard drug, i.e., fluconazole, against A. niger and C. albicans, respectively.     

Preparation of potentially bioactive aza and thiaza polycyclic compounds containing a bridgehead nitrogen atom. Synthesis of pyrrolo[1,2,3-de]-1,4-benzothiazine derivatives

The synthesis of some pyrrolo[1,2,3-de]-1,4-benzothiazine derivatives by using a modified Bischler type cyclization of N-(2,2-diethoxyethyl)-2H-1,4-benzothiazines as a crucial step is described. The alternative approach based on Friedel-Crafts alkylation of the N-(2-chloroethyl)-2H-1,4-benzothiazines is shown to be impractical due to the low yield obtained.     

Synthesis of 5,6- and 5,7-dichloro-3-methyl-4H-1,4-benzothiazines and their conversion into sulfones

A one pot synthesis of 5,6- and 5,7-dichloro-3-methyl-4H,4-benzothiazines is reported by the condensation and oxidative cyclization of 2-amino-3,4- and 3,5-dichlorobenzenethiols with β-dicarbonyl compounds. The oxidation of 4H-1,4-benzothiazines by 30% hydrogen peroxide in glacial acetic acid has provided the corresponding sulfones. The effect of the conversion of the sulfide linkage to sulfone is discussed. The structure of all the newly synthesized compounds has been confirmed by elemental analysis and spectral studies.     

REACTION BETWEEN 2,2′-DITHIODIANILINE AND FIVE-MEMBERED RING KETONES

Abstract

The acid-catalyzed reaction between 2,2′-dithiodianiline (1) and various five-membered ring ketones yields, in the absence of oxygen, the expected 1,4-benzothiazines. On exposure to air, the latter undergo an autoxidation process, according to a previously described general pathway. From the autoxidation of 12, the hemithioketal 16 has been isolated, and its peculiar properties are discussed.     

A study of the synthesis and some reactions of 3-phenyl-1,4-benzothiazines

Condensation of o-aminothiophenol with 2-bromoacetophenone yields 3-phenyI-1,4-benzo-thiazine hydrobromide, which upon treatment with alkali gave a mixture of 3-phenyl-2H-1,4-benzothiazine (VIIa) and 3-phenyl-4H-1,4-benzothiazine (VIIb). Catalytic hydrogenation led to rearrangement of the benzothiazine (VIIa) to 2-phenyl-2-methyl-2,3-dihydrobenzothiazole (X), while reduction with lithium aluminium hydride resulted in 3-phenyl-2,3-dihydro-4H-1,4-benzothiazine (XVI). The latter was transferred to 3-phenyl-4-aminoalkyl-2,3-dihydro-4H-1,4-benzothiazines (XVII and XVIII).     

η6-Arenetricarbonylchromium(0) Complexes in the Synthesis of 1,4-Benzodiazepines and Its Nucleophilic Substituted Products

Abstract

7-Chloro-5-carbomethoxy-1,3-dihydro-2H-1,4-benzodiazepines and its nucleophilic substituted products were synthesized via η⁶-arenetricarbonylchromium(0) intermediates. Ring enlargement of 5-chloro-N-chloroacetylisatin with hexamine in presence of Cr(CO)₆ led to the formation of 7-chloro-5-carbomethoxy-1,3-dihydro-2H-1,4-benzodiazepine in good yield with reduced reaction time. Nucleophilic substitutions on arene ring of η⁶-arenetricarbonylchromium(0) complexes with thiols, phenol, and primary amines were successfully carried out in decalin medium.     

1,4-benzothiazine derivatives from 2-aminobenzenethiol and hydrazonoyl halides

2-Aminobenzenethiol was condensed with alkyl α-chlorophenylhydrazonoglyoxylates yielding alkyl 2-(2-aminophenylthio)-2-arylhydrazonoglyoxylates which were cyclized to the corresponding 2-arylhydrazono-2,3-dihydro-4H-1,4-benzothiazin-3-ones. Starting from α-chloro-α-arylhydrazonoacetones the corresponding 2-arylhydrazono-3-methylbenzo-1,4-benzothiazines were formed.     

Design and synthesis of 4H-1,4-benzothiazines containing thiazole ring system for use as potential biopharmaceuticals

Synthesis of 4H-1,4-benzothiazines containing thiazole ring system is reported by condensation of substituted 2-amino-benzenethiols with N-(substituted benzothiazol-2-yl)-3-oxo-butyr-amides in the presence of DMSO.