Kumar Ranjan Bhushan

A Novel Route to 1,2,4-Triazoles

Abstract A novel synthetic method for the synthesis of 1,2,4-triazoles have been described starting from 1,3,4-thiadiazoles by adsorbing on acidic alumina under microwave irradiations (MWI).

MICROWAVE ASSISTED SYNTHESIS OF NOVEL 1,2,4-TRIAZINES IN “DRY MEDIA”

An efficient facile and solventless synthesis of 1,2,4-triazines using microwave is described. A non conventional synthetic procedure has been developed where solid inorganic support is used as energy transfer medium under microwave irradiation (MWI) which devoids hazards of solution phase reactions. The reaction time has been brought down from hours to seconds with improved yield as compared to conventional heating.

Microwave-Assisted Solid-Phase Synthesis of Cephalosporin Derivatives with Antibacterial Activity

Summary. The reaction of heterocyclic acids with 7-amino-cephalosporanic acid adsorbed on basic alumina under microwave irradiation afforded the N-acylated cephalosporin analogues in satisfactory yield. All compounds were tested for their antibacterial activity; some of them showed significant antibacterial properties. Cefotaxime and cephalothin were used as reference drugs.

Microwave Activated Solid Support Synthesis of New Antibacterial Quinolones

Summary. A novel synthesis of 6-fluoro-7-(5-aryl-1,3,4-thiadiazol/oxadiazol-2-yl-sulfanyl)-4-quinolone-3-carboxylic acids from 7-chloro-6-fluoro-4-quinolone-3-carboxylic acid and 5-substituted 1,3,4-thiadiazoles/oxadiazoles on basic alumina under microwave activation is described. All compounds were screened for their in vitro antibacterial activity against B. lichenformis, 2689, K. aerogens 2281, S. typhimurium 2501, E. herbicola 2491, and P. vulgaris 2027 and found to possess activities comparable to that of the standard drug norfloxacin.

Microwave assisted synthesis of novel organomercurials in ‘dry media’

Abstract New organomercurials of benzoquinone, barbituric acid and thiobarbituric acid with substituted aryl mercuric chloride have been synthesised using microwave irradiation under dry conditions in a domestic microwave oven in a few minutes with improved yields as compared to conventional heating. These organomercurials have a 1:1 stoichiometric ratio of aryl mercury and benzoquinone/barbituric acid/thiobarbituric acid moiety.

Synthesis of novel fungicidal organomercurials using microwaves

SummaryMercury derivatives of substituted 1,3,4-thiadiazoles and 1,2,4-triazine have been synthesized under microwave irradiation in open vessels using a domestic microwave oven as well as in a conventional way. The reaction time could be cut down from hours to minutes employing microwaves, accompanied by marginally improved yields. The compounds show promising fungicidal activity.ZusammenfassungQuecksilberderivate substituierter 1,3,4-Thiadiazole und 1,2,4-Triazine werden sowohl unter der Einwirkung von Mikrowellen (offene Gefäße, Haushaltsmikrowellenherd) als auch auf konventionelle Weise hergestellt. Die Anwendung von Mikrowellen verkürzt die Reaktionszeit von Stunden auf Minuten, die Ausbeuten steigen geringfügig. Die Verbindungen zeigen vielversprechende fungizide Aktivität.

Microwave Induced Synthesis of Ferrocenyl Substituted 1,2,4-s-Triazolo[3,4-b]-1,3,4-thiadiazoles

Summary. 5-Substituted 4-amino-3-mercapto-1,2,4-s-triazoles were synthesized from their corresponding hydrazides. Their condensation with ferrocene carboxylic acid in presence of phosphorus oxychloride under microwave irradiation afforded 3-substituted 6-ferrocenyl-1,2,4,-s-triazolo[3,4-b]-1,3,4-thiadiazoles. All new compounds were characterized on the basis of analytical and spectroscopic data. Reaction rates and yields were considerably enhanced using microwaves.Zusammenfassung. In Stellung 5 substituierte 4-Amino-3-mercapto-1,2,4-s-triazole wurden aus den entsprechenden Hydraziden dargestellt. Ihre Kondensation mit Ferrocencarbonsäure in Gegenwart von Phosphoroxychlorid unter Mikrowellenbestrahlung ergab in Position 3 substituierte 6-Ferrocenyl-1,2,4-s-triazolo[3,4-b]-1,3,4-thiadozole. Alle neuen Verbindungen wurden durch ihre analytischen und spektroskopischen Daten charakterisiert. Reaktionsgeschwindigkeiten und Ausbeuten wurden durch die Verwendung von Mikrowellen deutlich erhöht.

Deacylation of Cephalosporins by Lipase Catalysis and Microwave Assisted Transformation on a Solid Support

Deacylation of cephalosporins has been investigated using enzymatic and microwave activated solid phase techniques. The lipase calatysed deacylation was achieved under cooling with good yields but the microwave method was much faster with better yields. All the synthesised compounds were screened for their antibacterial activity and showed good results.

Microwave Assisted Stereoselective Synthesis and Antibacterial Activity of New Fluoroquinolinyl-β-lactam Derivatives

Summary. A series of quinoline ring substituted N-(3-chloro-2-(2-fluoro-quinolin-3-yl)-4-oxo-azetidin-1-yl)-octanamides were synthesized from chloroacetyl chloride, octanoic acid, (2-fluoro-quinolin-3-yl-methylene)-hydrazides, and triethylamine using microwave irradiation as well as conventional heating. The reaction time can be brought down from hours to minutes with improved yields using microwave irradiation compared to conventional heating. The compounds were tested for their in vitro antibacterial activity against 2253-Corynebacterium rubrum, 2340-Enterobacter, 2491-Erwinia herbicola, K12-E. coli, and 2873-Z. mobilis. and found to possess activities comparable with or superior to the standard drug ampicillin.Zusammenfassung. Eine Reihe von am Chinolinring substituierten N-(3-Chlor-2-(2-fluorchinolin-3-yl)-4-oxo-azetidin-1-yl)-octanamiden wurden durch Erhitzen der entsprechenden Octansäurehydrazide mit Mikrowellen oder auf konventionelle Weise dargestellt. Die Reaktionszeit wurde durch die Anwendung von Mikrowellen von Stunden auf Minuten reduziert, wobei die Ausbeuten höher lagen. Die Verbindungen wurden auf ihre in vitro-antibakterielle Aktivität gegen 2253-Corynebacterium rubrum, 2340-Enterobacter, 2491-Erwinia herbicola, K12-E. coli und 2873-Z. mobilis getestet. Dabei wurde gefunden, daß ihre Aktivität vergleichbar bzw. besser als jene des Standardwirkstoffs Ampicillin ist.

ALUMINA-SUPPORTED SYNTHESIS OF THIADIAZOLYL THIAZOLOTHIONES

The expeditious solventless synthesis of 3-[5′-alkyl-1′3′4-thiadiazol-2-yl]-4-phenyl/hydroxy-2-thiazolothiones is described from readily accessible 2-amino-5-alkyl-1,3,4-thiadiazoles on basic alumina that are accelerated by exposure to microwaves.