Arpita Das Gupta

Two efficient and green methods for synthesis of 4,4′-(arylmethylene)bis(1H-pyrazol-5-ols) without use of any catalyst or solvent

Two efficient and green methods for synthesis of 4,4′-(arylmethylene)bis(1H-pyrazol-5-ols) without use of any catalyst or solvent have been developed simply by heating (at 120°C) or microwave irradiation (300 W) of intimate mixtures of 3-methyl-l-phenyl-5-pyrazolone and aldehyde in 2:1 mole ratio.

One-pot Synthesis of 2,3-Dihydroquinazolin-4(1H)-ones under Catalyst- and Solvent-free Conditions

Small heterocyclic rings constitute one of the richest sources of diversity for medicinal chemists and more than half of biologically active molecules belong to various categories of quinazolinones. Among them, 2,3-dihydro-4(1H)-quinazolinones remain a major source for the design of therapeutic drugs. Moreover, they are building blocks for more than 150 naturally occurring pharmacologically active alkaloids and commercial drugs. Their pharmaceutical character include anti-malarial, anti-bacterial, anti-tumor, anticancer, anti-fungal, anti-convulsant and monoamine oxidase inhibitory activities. There are a number of methods for preparation of this class of compounds, the most direct one involving the condensation of aryl, alkyl, and heteroaryl aldehydes with anthranilamide in the presence of catalysts and solvents such as NH4Cl, 11 NaHSO4, b-cyclodextrin, cellulose-SO3H, 14 Amberlyst 15, [PYC4SO3H][HSO4]/A300SiO2, 16 Sc(OTf)3, 17 heteropoly acids, cyanuric chloride, transition metal-carbon nanotube (M-CNT) nanocomposites, 2-morpholinoethanesulfonic acid, 22 propylphosphonic anhydride (T3P ), K3PO4.H2O, 24 p-sulfonic acid calix[4]arene or trifluoroethanol. All of these reactions are successful in producing the target compound although certain drawbacks, such as use of harmful solvents, expensive catalysts, and low yields, are associated with some of them. With the goal of making some of the above-mentioned methods benign, the reactions were carried out under solvent-free conditions, using MW-irradiation and of water or ethanol as solvents. However, none of them proceeded without the use of catalyst. The current trend towards development of catalystfree and solvent-free reaction conditions encouraged us to study the same reaction without the use any catalyst or solvent. The remarkable success obtained in this investigation is presented herein. Our present methods involve subjecting an intimate mixture of anthranilamide and aldehyde/ketone (1:1 mole ratio) directly to heat (120 C, 10 min) or microwave (300 W, 3 min) irradiation. The time and temperature for the thermal reaction and the time and power for the MWI process were then optimized (Table 1). A range of structurally diverse aryl and heteroaryl aldehydes and two cyclic ketones were examined and gave the target compounds 3 (Scheme 1) in yields greater than 90% (Table 2). In the methods reported, it was a common observation that the reactions were very clean, and no side-products were formed in any run. In fact, the crude products obtained were of high purity and did not require any chromatographic separation; crystallization

A simple synthesis of E-9-aryl-5-arylidene-1-oxo-1,2,3,4,5,6,7, 8-octahydroxanthenes and their lower analogues from E,E-α,α′-diarylidenecycloalkanones

AbstractA simple and efficient synthesis of E-9-aryl-5-arylidene-1-oxo-1,2,3,4,5,6,7,8-octahydroxanthenes and their lower analogues has been developed by amberlyst–15 catalysed cyclocondensation of E,E-α,α′-diarylidenecyclohexanones and E,E-α,α′-diarylidenecyclopentanones, respectively, with cyclohexan-1,3-diones. The products were obtained in moderate to good yield and their structures were confirmed from analytical and spectral data. Graphical AbstractA simple and efficient synthesis of E-9-aryl-5-arylidene-1-oxo-1,2,3,4,5,6,7,8-octahydroxanthenes and their lower analogues has been developed by amberlyst-15 catalysed cyclocondensation of E,E-α,α′-diarylidenecyclohexanones and E,E-α,α′-diarylidenecyclopentanones, respectively, with cyclohexan-1,3-diones in anhydrous acetonitrile.

Facile Iodine-Catalyzed Michael Addition of Indoles to α,α'-Bis(arylmethylene)cyclopentanones: An Efficient Synthesis of E-2-(3-Indolylphenylmethyl)-5-phenylmethylenecyclopentanones.

Iodine-catalyzed reaction of indoles with α,α′-bis(arylmethylene)cyclopentanones afforded one diastereomer of the corresponding Michael adducts, namely, E-2-(3-indolylphenylmethyl)-5-phenylmethylenecyclopentanones, in a good yield. The products form a new group of indole derivatives.