Chayan Guha

A convenient, eco-friendly, and efficient method for synthesis of bis(3-indolyl)methanes “on-water”

Abstract A convenient, eco-friendly, and efficient method for synthesis of bis(3-indolyl)methanes by the reaction of indoles with various aromatic aldehydes “on-water” has been developed. The attractive features of this method are that in cases of aldehydes which are easily oxidized to acids, no external catalyst is necessary while in other cases a trace amount (ca. 5 mol%) of commercially available and inexpensive catalyst benzoic acid is sufficient to give good to excellent yield of products.

An efficient synthesis of 1,3-dimethyl-5-(2-phenyl-4H-chromen-4-ylidene) pyrimidine-2,4,6(1H,3H,5H)-triones and investigation of their interactions with β-lactoglobiulin

An efficient method for synthesis of 1,3-dimethyl-5-(2-phenyl-4H-chromen-4-ylidene)pyrimidine-2,4,6(1H,3H,5H)-triones has been developed by treatment of 2-hydroxychalcones and 1,3-dimethylbarbituric acid in refluxing toluene in the presence of amberlyst-15 as catalyst in air. The process involves the occurrence of a domino sequence of Michael addition, cyclization and aerial oxidation. The compounds synthesized showed an interesting property of free rotation around the bond linking the two heterocyclic moieties and three of them were found to show binding property with the milk protein β-lactoglobulin (β-lg). DFT and docking (with β-lg) studies of one of the compounds have been done.

A facile synthesis of 2-aryl-4-(indol-3-yl)-4H-chromenes using amberlyst-15 as an efficient recyclable heterogeneous catalyst

Starting from 2-hydroxychalcones and indoles, a facile synthesis of 2-aryl-4-(indol-3-yl)-4H-chromenes has been achieved by use of amberlyst-15, a sulfonated polystyrene resin, as a recyclable heterogeneous catalyst. The methodology involves a domino sequence of Michael addition, cyclization, and dehydration.Graphical abstract

Two expedient ‘one-pot’ methods for synthesis of β-aryl-β-mercaptoketones over anhydrous potassium carbonate or amberlyst-15 catalyst

AbstractTwo expedient one-pot methods have been developed for synthesis of β-aryl-β-mercaptoketones using acetophenones, benzaldehydes and thiols as starting materials. The methods involve microwave irradiation (5 min) of 1:1 mixtures of acetophenones and benzaldehydes over neutral alumina supported anhydrous potassium carbonate or amberlyst-15 in the first step, and that is followed by addition of thiol to the resulting material and keeping at room temperature for 1.5 h. Graphical AbstractAnhydrous potassium carbonate and amberlyst-15 are found to be efficient catalysts for the synthesis of β-aryl-β-mercaptoketones from acetophenones, benzaldehydes and thiols under solvent-free conditions. The experimental procedure is simple, involves shorter reaction times and results in good to excellent yield of the products.

An efficient three-component synthesis of coumarin-3-carbamides by use of Ni–NiO nanoparticles as magnetically separable catalyst

An efficient and ecofriendly synthesis of coumarin-3-carbamides, a class of compounds known for their remarkable biological activities and fluorescent properties, has been developed by a three-component reaction of 2-hydroxybenzaldehydes, aliphatic primary/secondary amines and diethyl malonate using Ni–NiO nanoparticles as catalyst in the green solvent ethanol. The method is compatible with various functional groups and moieties.

Simple Diastereoselective Synthesis of (2S*,2′R*,3′R*,4S*)-2,3′-Diphenylspiro[chroman-3,2′-oxiran]-4-ols and (2S*,2′S*,3′S*,4S*)-2,3′-Diphenylspiro[chroman-3,2′-oxiran]-4-ols

Oxiranes (epoxides) are very versatile building blocks in organic synthesis, and they can be opened up with a wide range of nucleophiles. Nucleophilic addition to epoxides plays a pivotal role in the stereoselective preparation of 1,2-difunctional compounds. It has been one of the most thoroughly studied reactions of epoxides, and for this different promoters and conditions have been developed. 1,3-Disubstituted and 1,2,3-trisubstituted 2,3-epoxyalcohols belong to an important group of epoxy compounds, as opening of their epoxy ring can lead to interesting compounds having three contiguous stereogenic centers. This fascinating aspect is the key factor for their use as precursors for the synthesis of a wide range of important and useful organic molecules. Two main routes for synthesis of 2,3-epoxyalcohols are i) epoxidation of allyl alcohols, and ii) chemoselective ketone reduction of a,b-epoxyketones. Both allyl alcohols and a,b-epoxyketones are readily available compounds, and those belonging to the latter type are generally prepared by a very simple reaction, viz., epoxidation of a,b-unsaturated ketones with hydrogen peroxide and alkali. It is worthwhile to mention here that for the reduction of a,b-epoxyketones, along with the chemoselectivity, the stereoselectivity of the reactions plays a very important role in the transformation steps necessary for achieving the targeted synthesis. This has led to the development of a good number of methods for chemoselective and stereoselective reduction of a,b-epoxyketones. E-3-Benzylideneflavanones (1) prefer a conformation in which the 2-aryl group is axially oriented. Sodium borohydride reduction of 1, studied in our laboratory, was

On the regioselectivity of the amberlyst-15 catalyzed condensation of 2-hydroxychalcones and 4,4-dimethylcyclohexane-1,3-dione

Abstract Amberlyst-15 catalyzed condensation of 2-hydroxychalcones and 4,4-dimethylcyclohexane-1,3-dione in refluxing toluene was found to show regioselectivity resulting in (6R*,12S*)-2,2-dimethyl-6-phenyl-2,3,4,12-tetrahydro-1H-6,12-methanodibenzo[d,g][1,3]dioxocin-1-ones as the major product.Graphical abstract

Base-promoted cyclocondensation of (1E,4E)-1,5-diarylpenta-1,4-dien-3-ones with guanidine hydrochloride: facile synthesis of E-2-amino-4-aryl-6-(2-arylethenyl)pyrimidines

Submit Manuscript | http://medcraveonline.com classes of pyrimidines. The pharmaceutical importance of these compounds lies on the fact that they can be effectively used as analgesics, anti-inflammatory, anticonvulsant, insecticidal, herbicidal, antitubercular, anticancer and antidiabetic agents [4-6]. Also, the pyrimidine and aminopyrimidine structures are frequently-occurring motifs in commercially available drugs such as anti-atherosclerotic aronixil [7], anti-anxiolytic buspirone [8], and other medicinally relevant compounds [9,10]. Symmetrical (1E,4E)-1,5-diarylpenta-1,4-dien-3-ones (1) and their unsymmetrical analogues (2), which could be constructed easily, also possess structural features similar to α,α’-bis(arylmethylene) cycloalkanones previously utilized by us for studying their reaction with thiourea and guanidine hydrochloride [11,12]. It is evident from the literature that the reaction of (1E,4E)-1,5diarylpenta-1,4-dien-3-ones (1 and 2) with guanidine has not been studied so far, although there are reports of cyclocondensation of varieties of α,β-unsaturated ketones with guanidine [13,14]. In this paper, we report a facile synthesis of E-2-amino-4-aryl-6-(2arylethenyl) pyrimidines by base-promoted cyclocondensation of various (1E,4E)-1,5-diarylpenta-1,4-dien-3-ones with guanidine hydrochloride.

3-[4-Bromo-α(R*)-methoxybenzyl]-6-chloro-3(S*),4(S*)-dihydroxychroman: X-ray and DFT Studies

Sodium borohydride reduction of E-3-benzylidenechromanone epoxides in dry methanol has afforded 3(S*), 4(S*)-dihydroxy-3-[α(R*)-methoxybenzyl]chromans as an interesting class of products, the structures of which have been assigned mainly from spectral data and consideration of the mechanistic aspects. X-ray diffraction study of one of them, 3-[4-bromo-α(R*)-methoxybenzyl]-6-chloro-3(S*),4(S*)- dihydroxychroman, is performed. The title compound crystallizes in the monoclinic sp. gr. P21/n, with a = 13.336(6) Å, b = 10.866(5) Å, c = 27.166(11) Å, β = 95.193(6)°, V = 3920(3) Å3, and Z = 8. Supramolecular construction of the compound involves O–H···O intermolecular hydrogen bonds as well as three other types of non-covalent interactions which are responsible for crystal packing. Density functional theory was applied for geometry optimization, molecular orbital calculations, and prediction of UV spectral features. The geometric parameters (bond lengths, bond angles, and dihedral angles) for the representative compound obtained from density functional theory with B3LY6-31G basis set were in good agreement with experimental values.