Microwave assisted organic synthesis-a review

Benzothiazole can serve as unique and versatile scaffolds, especially in synthetic and pharmaceutical chemistry because of their potent and significant pharmacological activities. This important class of derivatives possess numerous pharmacological activities like antitumor, antimicrobial, anti-inflammatory, anticonvulsant, antidiabetic activities and so on. Many scientists have developed a wide range of methodologies for the synthesis of the 2-substituted benzothiazole nucleus and its derivatives using different types of catalysts to improve the selectivity, purity and yield of the products. Thus, the present review article focuses mainly on the different kind of reactions involved in synthesis of the 2-substituted benzothiazole nucleus and its derivatives.

Recent advances in the synthesis of 2-substituted benzothiazoles: a review

Microwave activation coupled with dry media technique as a green chemistry procedure has been applied to synthesis of a series of some new title compounds. They have been obtained by the reaction of in situ synthesized 1,3-dihydro-3-[2-(phenyl/4-fluorophenyl)-2-oxoethylidene)-indol-2(1H)-one (4a, b) with substituted aminobenzenethiols (5a-d). The key intermediates 4a, b were also prepared in one step by this improved technique by reacting isatin and substituted acetophenones (2a, b). The results obtained under microwave irradiation when compared with that following conventional method demonstrate the versatility of the process. The title compounds 7a-e have also been screened for their antifungal and antitubercular activity, 7a and 7e showing maximum inhibition of growth of Alternaria alternata and Fusarium oxysporium and 7b, c, e revealing significant antitubercular activity.

Facile one pot microwave induced solvent-free synthesis and antifungal, antitubercular screening of spiro [1,5]-benzothiazepin-2,3'[3'H]indol-2[1'H]-ones.

Dry-media one-pot syntheses of fluorinated-2,3-dihydro-1,5-benzothiazepines under microwave activation

This review article deals with synthesis and reactions of benzo[1,5]thiazepines and the related derivatives and their applications, biological activity as well as spectroscopic data. Most of the reported data on the methods of synthesis, chemical reactions, and biological activity of these heterocycles published over the last ten years are reviewed in this paper.

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Benzo[1,5]thiazepine: Synthesis, Reactions, Spectroscopy, and Applications

Synthesis and antimicrobial evaluation of some new fluorinated spiro[[1,5] -benzothiazepin-2,3′[3′H]-indol]-2′(1′H)-ones

The title compounds were synthesised by condensation of 3-alykl/aryl-4-amino-5-mercaptotriazole (II) and 5-substituted 2-aminothiophenols (IV) with appropriate 2-phenyl-1H-indole-3-carboxaldehyde (I) under microwave irradiation in the presence of piperidine/p-toluenesulphonic acid using ethanol/DMF as energy transfer media. The considerable increase in reaction rate with improved yield has been observed, using microwave as compared to classical method.

Microwave induced synthesis of 2-substitutedphenyl-3-(3-alkyl/aryl-5,6-dihydro-s-triazolo) [2,4-b] [1,3,4] thiadiazo 6-yl indoles and 2-phenyl-3 [2, substituted benzothiazole] derivatives and their fungicidal activity

A series of fluorinated spiro[1,5-benzothiazepin-2,3′[3′ H ]-indol]-2′(1′ H )-ones have been prepared by the reaction of 2-aminobenzene-thiols with 1,3-dihydro-3-[2-phenyl/(4-fluorophenyl)-2-oxoethylidene)-indol-2(1 H )-ones ( I ) under microwave irradiation in open vessels using ethylene glycol as energy transfer medium and thermally in absolute ethanol saturated with hydrogen chloride gas. The comparative studies indicated that the microwave assisted organic synthesis has advantages of significantly reduced reaction time, improved yields and cleaner reactions as compared to the conventional method. All synthesized compounds have been characterized by analytical and spectral data and were screened for their antifungal activity against Alternaria alternata and Fusarium oxysporium and antitubercular activity against Mycobacterium tuberculosis IVb (R = F, X = F) and IVe (R = F, X = CH 3 ) have shown above 90% inhibition in reducing fungal growth of A. alternata while IVa (R = H, X — F) has shown 98% antitubercular activity on primary screening.

I. J. Gupta

Papers

Synthesis and antimicrobial evaluation of some new fluorinated spiro[[1,5] -benzothiazepin-2,3′[3′H]-indol]-2′(1′H)-ones

Microwave induced synthesis of 2-substitutedphenyl-3-(3-alkyl/aryl-5,6-dihydro-s-triazolo) [2,4-b] [1,3,4] thiadiazo 6-yl indoles and 2-phenyl-3 [2, substituted benzothiazole] derivatives and their fungicidal activity

Synthesis and Antimicrobial Evaluation of Some New Fluorinated Spiro[[1,5]-benzothiazepin-2,3′[3′H]-indol]-2′(1′H)-ones.