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Xanthenones constitute one of the most important classes of the naturally occurring organic compounds produced by many microorganisms. They exhibit many biological activities e. g., antibacterial, analgesics, antipyretics, cofactors etc. Structurally, these are the linear tricyclic compounds usually having O-heteroatom and carbonyl group. The xanthenone scaffold can be considered as a privileged structure as a lead for the search of new bioactive molecules. Being of pervasive importance, their synthesis by conventional thermal methods has been the subject of many studies. The recent strategies in synthetic organic chemistry concerning the synthesis of novel organic compounds having diverse applications mainly aims at improvement in atom as well as cost efficiency, avoidance of toxic reagents, and reduction in waste. In this context, photochemical reactions are relevant both from economical as well as from ecological point of view and also obey the demands of “green chemistry” or of an “ideal synthesis”. This article presents a review on the synthetic methodologies of the xanthenones- thermal (2012 onwards) and photochemical in addition to our own work on their synthesis. more...

Some of the title compounds (III), synthesized via a Pictet—Spengler reaction, are found to be cytotoxic against prostate, lung, breast, and cervical cancer cell lines.

We describe here a simple and facile asymmetric Mannich reaction catalyzed by chiral Cinchona alkaloid based squaramide containing H-bond donor catalysts, wherein, the reaction of 1,3-diketones with isatin (N-Boc) ketimines led to the formation of 3-aminooxindole derivatives. These derivatives were obtained in high yields with excellent enantioselectivities under mild conditions using 3 mol% of the catalyst. This protocol provides valuable and easy access to chiral 3-substituted 3-aminooxindole derivatives. more...

The first total synthesis of a naturally occurring styryllactone secondary metabolite parvistone B has been achieved in five steps with an overall yield of 67 % from readily available trans-cinnamaldehyde. It exhibits cytotoxicity against different human tumour cell lines. Key features of our synthetic strategy include Maruoka asymmetric allylation, Sharpless epoxidation, ring-closing metathesis, and regioselective epoxide ring-opening. This synthetic strategy constitutes a step economical, atom economical and protecting group-free total synthesis. more...

A one pot strategy for the synthesis of fused benzoxazino[1,2,3]triazolyl[4,5-c]quinolinone derivatives 4a–4k via the reaction of 5-iodo-4-(prop-2-yn-1-yl)-2H-benzo[b][1,4]oxazin-3(4H)-one (3) with different aryl azides under copper and palladium catalysis in a ligand free condition is achieved. The reaction provided the desired fused triazoles in good to excellent yields. The synthesized derivatives were evaluated for their in vitro cytotoxic activity against MCF-7, A-549 and HeLa cancer cell lines using MTT assay. The cytotoxic activity results revealed that, compound 4d has shown a broad spectrum of activity against MCF-7 and A-549 with IC50 values of 11.18 ± 0.8 and 17.81 ± 0.6 μM, which are comparable to the standard drug, cisplatin. The remaining compounds have shown good to moderate activity against the tested cell lines. Based on the results obtained, a structure activity relationship (SAR) is discussed. more...

The α-oxoketene dithioacetals and 1,4-dithiane-2,5-diol a dimer of mercapto acetaldehyde, react in the presence of anhydrous potassium carbonate in boiling ethanol to yield the corresponding 2-(methylthio)-3-aroyl/heteroaroyl thiophenes in 55–70% overall yields. more...

A concise total synthesis of dendrodolides A–D (1–4) has been accomplished in 10 steps from commercially available (R)-propylene oxide and 3-buten-1-ol as starting materials. The key steps involved in the synthesis are Jacobsen hydrolytic kinetic resolution, epoxide ring opening with 2-allyl-1, 3-dithiane, Yamaguchi esterification and ring-closing metathesis (RCM). In addition, a series of ester derivatives were prepared utilizing Yamaguchi esterification at the C-3 position of the dendrodolide core and screened for their efficacy against cancer cell lines. more...

Synthesis of new air stable octahedral ruthenium(II) carbonyl complex bearing O, and N-bidentate benzhydrazone ligand is reported. It has been characterized by elemental analysis, spectral methods and single crystal X-ray diffraction method. The new catalyst has been effectively applied to the transfer hydrogenation reaction of various ketones using isopropanol as a solvent and KOH as a base at 82 °C and the maximum conversion is achieved up to 100%. more...

A general approach involving the insertion of in situ generated aryne into the C–C bond of cyclic 1,3-diketones for rapidly assembling functionalized benzo-fused medium ring carbocycles is delineated. The efficacy of the methodology has been demonstrated through a concise total synthesis of pentacyclic natural product radermachol. more...

An efficient method was developed for the diastereoselective synthesis of novel fused dihydro-1H-furo[2,3-c]pyrazole by a one-pot, four-component reaction of β-keto ester, hydrazine, aromatic aldehyde, and pyridinium ylide in the presence of triethylamine under microwave irradiation in solvent-free conditions in good yields. The merits of this cascade Knoevenagel condensation/Michael addition/cyclization sequence include its high atom economy, good yields, and efficiency of producing three new bonds (two C–C and one C–O) and two stereocenters in a single operation. more...

Methyl phenyl sulfoximine is used as a directing group in the ruthenium-catalyzed intramolecular hydroarylation of alkene-tethered benzoic acid derivatives to afford dihydrobenzofurans and indolines. more...

The α-fluoro-α-oxoketenedithioacetals 3a–l have been synthesized by two routes. In Route 1 the pre-constructed α-oxoketenedithioacetals 1a–l are subjected to fluorination using selectfluor 2 to yield the corresponding stable α-fluoro-α-oxoketenedithioacetals 3a–l in 61–75% overall yields. In Route 2 a four-component one-pot protocol was followed involving addition of a mixture of active methylene ketone and carbon disulfide to sodium tert-butoxide suspended in tetrahydrofuran and dimethylformamide followed by addition of dimethyl sulfate and selectfluor sequentially to yield the corresponding 3a–l in an improved 79–87% overall yields. more...

A clean, cost-effective and very practical approach has been disclosed for the one-pot, cyclo condensation of aromatic aldehydes with different thiosemicarbazides in aqueous ethanol leading to pharmaceutically diverse 5-aryl-1,2,4-triazolidine-3-thiones in good yields under neutral reaction conditions. Simple operational procedure, high product yield, rapid and use of green solvent system make this protocol economical as well as environmentally benevolent. more...

β-oxodithioates react with bromoacetaldehyde diethylacetal in the presence of anhydrous potassium carbonate in dimethyl formamide at 80 °C to yield the corresponding mixed acetals. These acetals undergo smooth cyclization in the presence of ethanolic orthophosphoric acid to afford the corresponding 2-methylthio-3-acyl/aroyl/heteroaroyl thiophenes in 64–85% high overall yields. more...

Synthesis of a new family of air stable palladium(II)benzhydrazone complexes of the general formula [PdCl(PPh3)(L)] (where HL = thiophene aldehyde benzhydrazones) incorporating PPh3 and chloride as co-ligands has been described through a single and convenient step with good yields. All the new complexes have been fully characterized by means of elemental analysis, IR, UV-vis, and NMR spectral methods. The molecular structures of three of the complexes were determined by single crystal X-ray crystallography, which confirm the coordination mode of benzhydrazone and reveal the presence of a distorted square planar geometry around the Pd ion. The complexes 1–5 (0.05 mol%) have been found to be a highly active catalytic system in the mono and double Suzuki–Miyaura cross coupling reaction of deactivated aryl and heteroaryl bromides with different types of aryl boronic acids in neat water and the maximum yield was up to >99%. Notably, these catalysts work well with ultra-low loading of the catalysts and show high turnover numbers in a short time towards different substrates. Moreover, the catalysts could be simply recovered and reused five times without significant loss of efficiency. more...

An efficient method was developed for the synthesis of dihydrofuran substituted coumarin from a one-pot, four-component reaction of 2-hydroxy aromatic aldehydes, 6-methyl, 4-hydroxy pyranone, aromatic aldehyde, and pyridinium ylide in the presence of tri-ethylamine under microwave irradiation. The reaction proceeds under solvent-free conditions to afford C3-dihydrofuran substituted coumarin in a diastereoselective manner in good yields (71–89%). more...

An elegant, mild and straightforward methodology was explored for the first time towards the synthesis of polyfunctionalized pyrroles using β-cyclodextrin as a reusable supramolecular catalyst in aqueous medium. The present method provides various diversely substituted pyrroles from the commercially available synthons in good to excellent yields. The advantages of this novel protocol are use of environmentally benign reaction medium and recyclability of β-cyclodextrin over the existing methods. more...

Polycrystalline sample of Bi 2 Cu 5 B 4 O 14 was synthesized and its structural and magnetic properties were investigated by means of temperature dependent x-ray diffraction, magnetization, and heat capacity measurements. Bi 2 Cu 5 B 4 O 14 is found to be a spin-1/2 layered compound with repeating Cu-pentamer units. DC magnetic susceptibility at high temperatures follows the Curie-Weiss law with a large and negative Curie-Weiss temperature θ CW ≃ −39 K, suggesting the dominant ferromagnetic interaction between Cu 2+ ions. A positive curvature in inverse susceptibility and a magnetization hysteresis with reduced ordered moment at T = 2.1 K pinpoint the ferrimagnetic nature of the compound with T C ≃ 25 K. The modified Arrott analysis shows that Bi 2 Cu 5 B 4 O 14 is a good example of Heisenberg ( β = 0.367 and γ = 1.388) ferrimagnet. Heat capacity data at low temperatures (i.e. in the ordered state) follows a power law ( γT α ) with a reduced exponent ( α ≃ 2.58). The change in magnetic entropy is calculated to be S mag ≃ 28 J/mol K at around 100 K which is close to the expected theoretical value of 28.81 J/mol K for Bi 2 Cu 5 B 4 O 14 . more...

In recent years the carbocation has re-emerged as a highly efficient Lewis acid catalyst for a variety of organic transformations. However, the goal of asymmetric carbocation catalysis has so far been out of reach mainly as a result of difficulties associated with the preparation of stable chiral carbocations. Here, we describe developments towards asymmetric carbocation catalysis based on the concept of chiral-anion-directed catalysis. Chiral tritylium salts can be conveniently prepared in situ by mixing trityl chloride derivatives with chiral phosphonate, phosphoramide, bis(sulfonyl)amide, and bis(sulfuryl)amide silver or sodium salts. It is shown that the bis(sulfuryl)amide/tritylium ion salt catalyzes the Diels–Alder reaction with an up to 53 % enantiomeric excess. more...

In this simple method for the preparation of the title compounds, only a small amount of CAN as catalyst is required.

Using β-cyclodextrin (β-CD) as a catalyst pyrimidine derivatives were synthesized for the first time in aqueous medium. β-CD is a recyclable, inexpensive, economically viable, non-toxic, and readily available material. Various aldehydes were used with ammonium acetate, and 1,3-diketones to generate a series of pyrimidine derivatives in good to excellent yields. more...

Asymmetric Michael addition of 3-methyl-2-pyrazolin-5-one to β-nitrostyrenes, catalyzed by a series of chiral squaramide bifunctional catalysts derived from cinchona alkaloids, yielded chiral pyrazol-3-ol derivatives. These pyrazol-3-ol derivatives were obtained in moderate to high yields with good enantioselectivities under mild conditions using 1 mol % of the catalyst. This reaction affords valuable and easy access to chiral 5-methyl-4-(2-nitro-1-arylethyl)pyrazol-3-ol derivatives. more...

(Methylthio) acroleins 1a–m were shown to be stable unlike their counterpart the chloroacroleins and their efficacy as 1,3-dielectrophilic properties have now been examined successfully in this work. They are shown to react with ethyl thioglycolate in the presence of anhydrous potassium carbonate in boiling ethanol to yield the corresponding 5-substituted/4,5-annulated-2-carbethoxy thiophenes in 70–80% overall high yields. more...

Since the re-emergence of multi-ferroics and magnetoelectrics almost a decade ago, bismuth ferrite has been among the most heavily studied model system. It is a multi-ferroic with robust ferroelect... more...

We report the first example of a very general Cu-catalyzed cross-coupling of organoaluminum reagents with organohalides. The reactions proceed for the couplings of alkyl-, aryl-, and alkynylaluminum reagents with aryl and heteroaryl halides and vinyl bromides, affording the cross-coupled products in good to excellent yields. Both primary and secondary alkylaluminum reagents can be utilized as organometallic coupling partners. These reactions are not complicated by β-hydride elimination, and as a result rearranged products are not observed with secondary alkylaluminum reagents even for couplings with heteroaryl halides under “ligand-free” conditions. Radical clock experiment with a radical probe and relative reactivity study of Ph3Al with two haloarenes, 1-bromonaphthalene and 4-chlorobenzonitrile, having two different redox potentials indicates that the reaction does not involve free aryl radicals and radical anions as intermediates. These results combined with the result of the Hammett plot obtained by r... more...

We report an efficient copper(I) iodide catalyzed cross-coupling­ of diarylzinc reagents with aryl iodides. The reaction proceeds under ligand-free conditions at low catalyst loading (5 mol%) and tolerates a variety of functional groups. more...

An unprecedented Pd-catalyzed cascade Wacker–Heck lactonization-cyclization sequence is reported. The process provides a facile approach to bi- and tricyclic spiranoid lactones in good yields. The reaction shows general substrate scope and a broad functional group tolerability. In addition, a rare 4-exo trig Heck-type cyclization is demonstrated. more...

A general, parallel, and collective synthesis of 5/5/5- and 5/5/6-ring fusion topologies of tricyclic spiranoid lactones through the controlled cyclizations of easily accessible, common key precursors is described. The rapid composition of key cycloalkyl methylene precursors yielded an assembly of bicyclic diastereoisomeric iodolactones, which were individually converted into a wide range of tricyclic, angularly fused spiranoid lactones in a regioselective and stereodirected fashion through the diastereoisomeric differentiation of a collective key precursor. The critical stereochemical assignment of the bicyclic starting materials, as well as the tricyclic targets, was confirmed by X-ray crystal structure determination. more...

A simple, efficient and green chemical ultrasound assisted thio-Michael addition reaction between thiols and (Z)-azlactones aiming to produce non-natural amino acid derivatives by using chiral Zn[(L)-Pro]2 as a heterogeneous catalyst is herein described. The product was obtained in good to excellent yields presenting high diastereoselectivity. more...

A α-cross-coupling aldol type addition reaction activated olefins with isatins has been described in the presence of ruthenium(III) chloride and tributyltin hydride (TBTH) at room temperature. This method is found to work consistently for the delivering of ene-carbonyl coupled products in good to excellent yields with moderate to acceptable selectivity. The substrate scope of the present method was briefly discussed. more...

The key N -homopropargylthiourea intermediates, N-substituted 2-oxo-4-propargylazetidine-1-carbothioamides, were prepared by the reaction of a 4-propargylazetidin-2-one with isothiocyanates. Bicyclic β-lactams, i.e. 3-thia-1-dethiacephems, were prepared via highly regioselective iodocyclization reaction of N-substituted 2-oxo-4-propargylazetidine-1-carbothioamides with molecular iodine at room temperature in moderate to excellent yields. A variety of functional groups were well tolerated under the reaction conditions. more...

We have developed the Cp*Rh(III)-catalyzed cyclization reaction of arylnitrones with diazo compounds to obtain N-hydroxyindoline products under mild conditions. The substrate scope and functional group compatibility were examined with the demonstration of synthetic utility. more...

An efficient copper-catalyzed π-activation protocol has been developed for the intramolecular hydroarylation of alkynes. The strategy has been used in atom-economical syntheses of β-carboline analogues. The cycloisomerized products were obtained in moderate to good yields. more...

A concise total synthesis of the four stereoisomers of (–)-pochonicine was undertaken. The key steps of the synthesis involved chemoselective debenzylation of the primary benzyloxy group and an unprecedented Na–Hg-mediated concomitant N-detosylative intramolecular epoxide ring-opening reaction. Notably, additional steps for the protection of other functional groups were not required. Glycosidase inhibition studies revealed that these compounds are inhibitors of β-N-acetylglucosaminidase with IC50 values in the sub-millimolar range. more...

3-Thia-1-dethiazephams (II) are synthesized in high regio- and stereoselectivity via iodocyclization reaction of alkene-thioureas (I).

Lithium rubidium borate (LiRbB4O7) single crystal has been grown by the Czochralski method. Crystalline perfection and optical homogeneity of the grown LiRbB4O7 crystal are analyzed by high resolution X-ray diffraction and birefringence interferometric technique, respectively. Third order nonlinear optical parameters of LiRbB4O7 crystal are determined by Z-scan experimental technique. The nonlinear refractive index (n2) and third-order nonlinear optical susceptibility (χ3) are estimated to be −4.935 × 10−11 cm2/W and 2.719 × 10−7 esu, respectively. The measured (n2) value reveals the self-focusing nature of LiRbB4O7 crystal. more...

A novel, simple and efficient synthetic protocol has been developed for the synthesis of spiro[indoline-3,4′-pyrano[2,3-c]pyrazole]-3′-carboxylate and trifluoromethylated spiro[indole-3,4′-pyrano[2,3-c]pyrazole] derivatives via a one pot, four-component reaction using recyclable polyethylene glycol (PEG-400). This new protocol produces novel spiro pyranopyrazole derivatives in good to excellent yields, with operational simplicity and recycling of PEG-400. The remarkable features of this methodology are high yields, an easy work-up process, and a greener method that avoids toxic catalyst and hazardous solvents. more...

A common protocol for the synthesis of amides, esters and α-ketoesters via cross dehydrogenative coupling of aldehydes and amines/alcohols has been developed. The method is applicable to a wide variety of alcohols and amines as well as aliphatic and aromatic aldehydes. Also, the use of acetaldehyde for acetylation and ethyl glyoxalate to access 2-oxo-amino esters is presented for the first time. more...

We report a Cu-catalyzed coupling between triarylaluminum reagents and alkyl halides to form arylalkanes. The reaction proceeds in the presence of N,N,N',N'-tetramethyl-o-phenylenediamine (NN-1) as a ligand in combination with CuI as a catalyst. This catalyst system enables the coupling of primary alkyl iodides and bromides with electron-neutral and electron-rich triarylaluminum reagents and affords the cross-coupled products in good to excellent yields. more...

Electrophilic halogenation is used to produce a wide variety of halogenated compounds. Previously reported methods have been developed mainly using a reagent-based approach. Unfortunately, a suitable "catalytic" process for halogen transfer reactions has yet to be achieved. In this study, arylamines have been found to generate an N-halo arylamine intermediate, which acts as a highly reactive but selective catalytic electrophilic halogen source. A wide variety of heteroaromatic and aromatic compounds are halogenated using commercially available N-halosuccinimides, for example, NCS, NBS, and NIS, with good to excellent yields and with very high selectivity. In the case of unactivated double bonds, allylic chlorides are obtained under chlorination conditions, whereas bromocyclization occurs for polyolefin. The reactivity of the catalyst can be tuned by varying the electronic properties of the arene moiety of catalyst. more...

The new title compound is synthesized in 95% yield from mixtures of Eu, Ir, excess In as an active metal flux, and Si to nucleate crystal growth (alumina crucible, 1273 K for 6 h, followed by annealing at 1123 K for 72 h). more...

An asymmetric synthesis of (I) is presented starting from (S)-2-hydroxypropanoate via Horner—Wadsworth—Emmons olefination, Sharpless dihydroxylation, zinc allylation, and ring-closing metathesis.

The enantiospecific conversion of chiral secondary boronic esters into alkylfluorides is reported. Boronate complexes derived from boronic esters and PhLi were used as nucleophiles, with Selectfluor II as the electrophilic fluorinating agent, to afford alkylfluorides in short reaction times. The addition of styrene as a radical trap was found to enhance enantiospecificity. A broad range of alkyl boronic esters were converted into alkylfluorides with almost complete enantiospecificity by this method. more...