J. Venu Madhav

3-[Benzimidazo- and 3-[benzothiadiazoleimidazo-(1,2-c)quinazolin-5-yl]-2H-chromene-2-ones as potent antimicrobial agents.

A series of 3-[benzimidazo(1,2-c)quinazolin-5-yl]-2H-chromene-2-one (6a-6f) and 3-[benzothiadiazole- imidazo(1,2-c)quinazolin-5-yl]-2H-chromene-2-one derivatives (7a-7f) that incorporate a variety of substituents at the 6- and/or 8-positions of the coumarin moieties have been synthesized utilizing cellulose sulfuric acid as an efficient catalyst under both conventional heating and microwave irradiation procedures. These analogs were evaluated for their antimicrobial activity against Bacillus subtilis, Staphylococcus aureus, Streptococcus pyogenes (Gram-positive bacteria), Escherichia Coli, Klebsiella pneumonia, Salmonella typhimurium (Gram-negative bacteria), and Aspergillus niger, Candida albicans, and Aspergillus flavus (Fungi). Two analogs, 6c (a 6,8-dichloro analog, MIC([SA]) = 2.5 μg/mL; MIC([ST]) = 2.5 μg/mL) and 7d (a 6,8-dibromo analog, MIC([ST]) = 2.5 μg/mL) were identified as potent antibacterial agents, and two analogs, 6b (a 6-bromo analog, MIC([AF]) = 10 μg/mL) and 6d (a 6,8-dibromo analog, MIC([AF]) = 15 μg/mL; MIC([CA]) = 15μg/mL), were identified as potent antifungal agents. Based on the MIC data, analogs 6b, 6c, 6d, and 7d were identified as the most potent antimicrobial agents in the series.

Expeditious Pechmann Condensation by Using Biodegradable Cellulose Sulfuric Acid as a Solid Acid Catalyst

A facile synthesis of coumarins was performed in excellent yields via Pechmann condensation by using different type of phenols and ethylacetoacetates under solvent–free media using both conventional method and microwave irradiation in short reaction times is described. The reaction workup is very simple, and the catalyst can be easily separated from the reaction mixture and reused several times in subsequent reactions.

Cellulose Sulfuric Acid: An Efficient Biodegradable and Recyclable Solid Acid Catalyst for the Synthesis of 1-Oxo-hexahydroxanthene

Abstract A series of 1-oxo-hexahydroxanthene derivatives was synthesized at room temperature in solid state from substituted salicylaldehydes and substituted 1,3-hexanediones in the presence of a catalytic amount of cellulose sulfuric acid. The results showed that the reaction performed under solid-state conditions was benign to the environment, with higher yields and more convenient workup.

CuPy2Cl2: A Novel and Efficient Catalyst for Synthesis of Propargylamines Under the Conventional Method and Microwave Irradiation

Abstract CuPy2Cl2 is an efficient catalyst for the preparation of propargylamines via three-component coupling reaction of aromatic aldehydes, amines, and aromatic alkynes stirred at 95 °C without using any solvent to afford the corresponding products in good yields. The reaction mixture was irradiated at 450 W in a microwave oven to furnish the expected products in excellent yields.

Cellulose Sulfuric Acid: Novel and Efficient Biodegradable and Recyclable Acid Catalyst for the Solid-State Synthesis of Thiadiazolo Benzimidazoles

Abstract An efficient method for the synthesis of 2-substituted benzimidazoles has been developed. In this method, benzo[c][1,2,5]thiadiazole-4,5-diamine was condensed with different aldehydes in the presence of cellulose sulfuric acid under solvent-free conditions by simple physical grinding of reactants using a mortar and pestle at room temperature. The methodology is mild, high-yielding, and green, and the catalyst could be easily recycled.

Solid-State Synthesis of 1,3-Selenazoles Employing CuPy2Cl2 as a Lewis Acid Catalyst

Abstract 1,3-Selenazoles were Synthesized from 3-bromo acetyl coumarin and selenourea in the presence of CuPy2Cl2 under solvent-free conditions at ambient temperature. The pure products were identified by spectral data.

Xanthan Sulfuric Acid: An Efficient and Recyclable Solid Acid Catalyst for Pechmann Condensation

Abstract In this report, substituted coumarins are formed via Pechmann condensation using various substituted phenols and ethyl acetoacetates in the presence of xanthan sulfuric acid as a solid acid catalyst under solvent-free conditions. This method is very simple, cost-effective, and has shorter reaction times, and the catalyst could be reused. GRAPHICAL ABSTRACT

Sulfamic Acid–Catalyzed One‐Pot Synthesis of 3‐(4,6‐Dimethyl‐oxazolo[4,5‐c]quinolin‐2‐yl)‐chromen‐2‐ones using the Conventional Method and Microwave Irradiation

Abstract A rapid and efficient method for the preparation of 3‐(4,6‐dimethyl‐oxazolo[4,5‐c]quinolin‐2‐yl)‐chromen‐2‐ones by the reaction between 3‐amino‐2,8‐dimethyl‐quinolin‐4‐ol and 2‐oxo‐2H‐chromen‐3‐carboxylic acid using sulfamic acid as a acid catalyst and dimethyl formamide as a solvent using the conventional method and microwave irradiation is reported.

Xanthan Sulfuric Acid: A New and Efficient Biosupported Solid Acid Catalyst for the Synthesis of 3,4-Dihydropyrimidin-2(1H)-Ones

Abstract Xanthan sulfuric acid (XSA) is employed as a recyclable catalyst for the synthesis of 3,4-dihydropyrimidin-2(1H)-ones. These syntheses were performed via a one-pot, three-component condensation of aldehydes, amines, and urea/thiourea under solvent-free conditions. GRAPHICAL ABSTRACT

Expeditious Synthesis of Thiadiazolo Benzodiazepines Under Conventional Method and Microwave Irradiation

This article explores the use of sulfamic acid as an efficient catalyst for the one-pot synthesis of thiadiazolo 1, 5 benzodiazepines by using benzo[c][1,2,5]thiadiazole-4,5-diamine and various types of ketones in the presence of chloroform as a solvent under conventional methods and microwave irradiation. Our method is more advantageous than current methods. The catalyst (sulfamic acid) is cost effective, readily available and gives excellent yields with high purity. In comparison, the microwave irradiation method is equally as effective with a shorter reaction time and still maintaining high yields.