Balbir Kaur

Ultrasound-promoted greener synthesis of 2H-chromen-2-ones catalyzed by copper perchlorate in solventless media.

Copper perchlorate is found to be a heterogeneous catalyst for an efficient and greener synthesis of 4-substituted 2H-chromen-2-ones via von Pechmann condensation of substituted phenols and beta-keto esters in solventless media with excellent yields using ultrasound irradiation. The present methodology offers several advantages such as excellent yields, simple procedure and milder conditions.

One-pot Solvent-free Sonochemical Synthesis of 1-Amidoalkyl-2-naphthols

In recent years, organic synthesis involving greener processes, including solvent-free conditions, has been explored due to stringent environmental and economic regulations. 1 Homogeneous, liquid a...

Ultrasound Promoted Cu(Clo4)2 Catalyzed Rapid Synthesis Of Substituted 1,2,3,4- Tetrahydropyrimidine-2-Ones & Hantzsch 1,4-Dihydropyridines In Dry Media

Copper perchlorate supported on bentonite clay as catalyst at room temperature gives 6-methyl-4-substituted-phenyl-2-oxo(thioxo)-l,2,3,4-tetrahydropyrimidine-5carboxylic acid ethyl esters & diethyl 2,6-dimethyl-4-substitutedphenyl-l,4dihydropyridine-3,5-dicarboxylate proficiently in high yields in solvent-less media under ultrasonic irradiation. Introduction Green chemistry protocols have shown significant potential as truly eco-friendly methodologies (1-2). Biginelli Compounds have exhibited pharmaceutical activities (3-6) whereas the 1,4-DHP motifs has been used as chemotherapeutic agents (7). The first synthetic method for the synthesis of l,2,3,4-tetrahydropyrimidine-2-ones (THPMs) was reported by Biginelli (8) under strongly acidic conditions producing THPMs, though in low yields. In view of the pharmaceutical significance of these compounds, many improved catalytic methods have been developed (9-13). In continuation of our studies (14) we wish to report an expedient procedure for the synthesis of l,2,3,4-tetrahydropyrimidine-2-one derivatives and Hanstzch 1,4 dihydropyridines from three-component condensation of aryl aldehydes, ethylacetoacetate and urea or thiourea or ammonium carbonate in solvent-less dry media (bentonite clay) supported-copper perchlorate as catalyst at room temperature under ultrasonic irradiation. Experimental Materials and Apparatus All melting points recorded are uncorrected, open capillary measurements, using sulphuric acid bath. IR spectra were recorded using KBr pellets on a Perkin-Elmer spectrophotometer, NMR spectra on AL-300F (Bruker) FT NMR spectrophotometer. Sonication was performed in ELMA, Transsonic T 310/H Ultrasonic cleaner (with a frequency of 35 KHz), Hans Schmidbauer GmbH & Co., Germany. The reactions were performed in open vessels. General procedure Synthesis of l,2,3,4-tetrahydropyrimidine-2-one derivatives la-f & Hantzsch 1,4 dihydropyridine derivatives 2a-f in solvent-less media: A mixture of aldehyde (0.010 mole), ethyl acetoacetate (0.015 mole) and urea or thiourea (0.012 mole) or ammonium carbonate (0.015 mole), in the presence of copper perchlorate (10% mmol) adsorbed on bentonite clay (5 gm) was placed in a sonicator under ultrasonic irradiation (completion of the reactions was monitored by TLC). To this crude reaction mixture was added ethyl alcohol (50 mL) and distilled water (5 mL). The mixture was stirred for 1 minute and then suction filtered. The spent reagent was

Copper Perchlorate Hexahydrate: An Efficient Catalyst for the Green Synthesis of Polyhydroquinolines under Ultrasonication

Copper perchlorate hexahydrate as an efficient catalyst was used for the synthesis of polyhydroquinolines by four-component condensation reaction of aldehyde, ethyl acetoacetate, dimedone, and ammonium acetate in excellent yields and short reaction times at room temperature under ultrasound irradiation. This novel synthetic method is especially favoured because it provides a synergy between copper perchlorate hexahydrate and ultrasound irradiation which offers the advantages of high yields, short reaction times, simplicity, and easy workup compared to the conventional methods reported in the literature.

Convergent One Pot Synthesis of Novel Thiazolo Pyrimidine and Their Antimicrobial Activities

One pot three component cyclocondensation of 2-amino-4-phenyl thiazole, ethyl benzoyl acetate and aromatic aldehydes produces Thiazolo Pyrimidine in moderate to good yields. Some of the compounds were screened for anti-bacterial (Staphylococcus aureus, Staphylococcus aureus (MRSA), Streptococcus pyogenes) and antifungal (Aspergillus niger) studies by Agar Diffusion method. Compounds show moderate to good antifungal activity but low antibacterial activity. INTRODUCTION Various 2-amino thiazole derivatives are of great importance to chemists as well as biologists as they exhibit a variety of biological activities like antibacterial1, antiviral2, anti-inflammatory3, antiallergies4 and antihypertensive5. The high scientific interest attracted by 3,4-dihydropyrimidines is due to broad spectrum of biological activities exhibited by these compounds like antihypertensive6, antioxidant agents7, antitumor activity8 and calcium channel modulation9. In 1893, Italian Chemist Pietro Bignelli10 synthesized 3,4-dihydropyrimidin-2(1H)-ones by heating a mixture of aldehyde, β-ketoester and urea in ethanol containing a catalytic amount of HCl. However, this procedure suffers from harsh reaction conditions, long reaction time and frequently low yield. Later on subsequent multistep synthesis furnished some what higher yield but these do not have the simplicity of original one pot protocol11. This paper reports a novel approach to the synthesis of thiazolo-pyrimidines. As thiazolo pyrimidines are classes of fused heterocycles that are of considerable interest because of their wide range of biological activities like anti cancer12, phosphate inhibitors13, antimicrobial14 and acetylcholinesterase inhibitors15. Various methods have been reported for the synthesis of thiazolo pyrimidine in literature16 which are associated with many drawbacks like multistep synthetic root, longer reaction time with drastic conditions, difficult workup, unsatisfactory yields and use of expensive & hazardous chemicals. Hence, here we report herein a general, single step and efficient approach towards the synthesis of thiazolo pyrimidines. Prompted by the observed biological activities of the above mentioned derivatives and in continuation of our research for thiazolo pyrimidines17, a rapid and efficient synthesis of a series of novel thiazolo pyrimidines and evaluation of their antimicrobial potency is being reported. RESULTS AND DISCUSSION Synthesis and characterization In view of the recent emphasis aimed at developing simple, highly efficient and one pot methodologies for the preparation of organic compounds, herein we report convergent one pot cyclocondensation of ethyl benzoyl acetate 1 ( 0.01 mole), thiazole 2 (0.01 mole), various substituted aromatic aldehydes 3 (0.01 mole) which give thiazolo pyrimidines 4 (Scheme 1). A variety of aromatic aldehydes carrying either electron donating or electron withdrawing substituents reacted very well, giving products in high purity. Scheme 1: synthesis of thiazolo pyrimidine

Microwave-Induced One-Pot Facile Synthesis Of Thiazolo-Pyrimidines Using Silica Gel As Solid Support

An efficient one-pot rapid synthesis of thiazolo-pyrimidines was carried out via Biginelli three component condensation reaction under microwave irradiations in a solvent-free media using Silica gel as solid support. The present method provides a high speed, efficient, environmentally benign modification of classical Biginelli reaction without using an expensive reagent. INTRODUCTION In 1893, Pietro Biginelli reported the first synthesis of 3,4-dihydropyrimidin-2(lH)-ones by a very simple one-pot condensation reaction of an aromatic aldehyde, urea and ethyl acetoacetate in ethanolic solution through thermal heating. Later on, lots of structural variations2 were carried out in dihydropyrimidines because of their resemblance to commercially used Hantzsch pyridines as antihypertensive agents. The present paper describes the synthesis of their bicyclic derivatives viz. thiazolo-pyrimidines. Thiazoles and pyrimidines individually or in combination are involved with a wide range of biological activities. They can act as antiviral, antitumoral, antimalarial, antifungal, antihypertensive, analgesic and antiinflammatory agents. The wider therapeutic application of thiazolo-pyrimidines derivatives prompted us to synthesize this class of compounds. Several conventional and non-conventional methods have been reported for the synthesis of thiazolo-pyrimidines. However, these methods are associated with many drawbacks like multistep synthetic route, longer reaction time with drastic conditions, difficult work up, low yield and use of expensive and hazardous chemicals. But, as the concept of one-pot multicomponent reaction and Microwave-induced organic reaction enhancement technique using dry media is gaining importance, due to increasing environmental and economical concerns, we have modified the synthetic route of the title compounds to one-pot multicomponent cyclocondensation reaction under microwave irradiations using solid support. As the solution phase microwave reaction have some limitations, like superheating of the solvent may result in explosion. The solid supports viz. alumina, silica gel, montmorillonite, etc. provide acidic, basic and neutral environment and they reduce the amount of toxic wastes and byproducts in chemical transformations. Through this modification, precious solvents can be saved, reaction time can be reduced and overall yield can be improved by reducing the no. of steps. Thus, it is a step towards green chemistry. RESULTS AND DISCUSSION The multicomponent reactions under microwave irradiation using dry media develop a facile protocol to generate library of several heterocyclic compounds in an environmentally benign fashion. In view of this, the synthesis pf the title compounds was carried out using these techniques. For this, thiazole was reacted with ethylacetoacetate and aromatic aldehydes using silica gel as solid support (Scheme 1). The reaction was completed in 1-6 min. A variety of