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The concept of a green approach has been applied in the reaction, separation and solidification of a single unit. The products, 2-benzimidazol-diphenyl-2-imino-thiazolidine-4-ols, are purely hemiaminals. They have a tendency to decompose at a high rate. The solid-phase reactive chromatographic technique has been applied to avoid extensive liquid–liquid extraction and stabilised the product by precipitation in solvents. Benzimidazole phenyl thiourea and phenacyl bromide have been used as starting materials in this study. Both the starting materials are adsorbed on dry silica and packed in a glass column with a systematic arrangement of layers. A directly solid product was precipitated in cold hexane. Anticancer activities have been recorded against four cell lines, human colon, prostate, lung and breast cancer, with reference to doxorubicin as a standard. These compounds show a promising effect on human lung cancer, products B9 (IC50 = 3.890 μM) and B10 (IC50 = 2.798 μM) and B13 (IC50 = 3.140 μM) which very close to doxorubicine (IC50 = 1.750 μM). It was observed that fluoro phenyl functionalities are effective compared to trifluoro methyl phenyl functionalities for anticancer activities. These small molecules lose their activities, except fluorination, on bulky substitution. This convenient metal-free approach is highly efficient for unstable hemiaminals such as the potent anticancer benzimidazol-diphenyl-2-imino-thiazolidine-4-ols.

Benzimidazol-amino thiazoles are synthesized under microwave irradiations using benzimidazole phenyl thiourea and 2-bromoacetophenone. Bifunctional hydrogen bonding plays an important role in chemical conversion. The reaction was carried out by C-C bond formation, followed by C-N bond cleavage and simultaneous migration of the benzimidazole ring. This reaction is novel and efficient for the synthesis of benzimidazol-amino thiazoles in which microwaves were used as driving forces. Synthesis of the product was controlled by double hydrogen bonding which is practically confirmed by the synthesis of routine imino-thiazole as an alternative product in the simple acidic condition. The simple acidic condition is neither responsible nor sufficient for optimum conversion of the benzimidazole migrated product. The synthesized products benzimidazole amino thiazoles D4 (IC50 = 4.207 μM) and D8 (IC50 = 2.398 μM) show interesting anticancer activities for human lung cancer with reference to doxorubicin (IC50 = 1.750 μM).

A novel, one-pot reaction for the synthesis of 3,4-dihydroisoquinolin-2(1H)-one derivatives is developed via a base-mediated three-component reaction of ninhydrin, aniline and acetylenic esters. This diastereoselective reaction takes place in methanol at 70 °C under transition-metal-free conditions, and direct construction of the C–N and C–C bonds is readily achieved via tandem cyclization. These cyclic frameworks are resourceful small molecular keys to many natural products.

Total synthesis of trocheliophorolide C epimer is reported. The synthetic strategy involves generation of lactone skeleton and preparation of unsaturated side chain followed by cross-metathesis. The Eglinton oxidative coupling, Cadiot-Chodkiewicz cross-coupling and cross-metathesis are the key reactions used in the synthesis. We also attempted the synthesis of trocheliophorolide D epimer, which includes Cu catalyzed various cross-coupling reactions.

Formal synthesis of 14-membered unsymmetrical bis-macrolactone, (−)-colletodiol was accomplished from homopropargylic alcohol derivative. Building of the two different hydroxy acid fragments from the same intermediate of homoallylic alcohol was particularly advantageous. A Sharpless asymmetric dihydroxylation, homologation of carbon chain, a Pinnick oxidation, and a macrolactonization to assemble the 14-membered macrodiolide were the additional salient features of this convergent synthesis.

The multicomponent reaction between isatin, amino acid, but-2-ynedioates, and phenacyl bromide has been developed using microwave irradiation under catalyst and base-free conditions in aqueous medium. This synthetic protocol is useful for the synthesis of various functionalized spirooxindole derivatives. This MCR exhibits a broad substrate scope with excellent yields and shorter reaction time. Additionally the synthesized spirooxindole derivatives were evaluated for their anticancer activity against three human cancer cell lines: MCF-7 (breast), A549 (lung), and HeLa cervical. Most of the compounds showed moderate to potent cytotoxic activity against the tested cell lines.

Stereocontrolled total synthesis of obolactone was achieved from trans- cinnamaldehyde. The key steps in this synthetic sequence are a asymmetric Mukaiyama Aldol, a Crimmins' modified Evans' Aldol reaction to introduce C2′ stereocentre, a nucleophilic addition of potassium salt of mono methyl malonate, a Z -olefination using Andos' modified Horner-Wadsworth-Emmons reagent to introduce Z -olefin at C3, C4 in the final lactone skeleton, and a tandem deprotection and lactonization.

Zn/CeCl3.7H2O mediated facile and an efficient synthesis of oxindoles motifs via linear regioselective reductive coupling between isatin/isatinimine derivatives and vinyl sulfones at room temperature has been described. This synthetic protocol is base free and allow for the synthesis of wide variety of oxindole motifs in moderate to high yields. This is the first example of Mannich-type coupling between isatinimines and vinyl sulfones.

A simple and novel method has been developed for the C6-functionalization of unprotected tetrahydroquinoline with chromenes or β-nitrostyrenes in aqueous medium to afford novel 6-substituted tetrahydroquinolines. This method is simple and convenient, and has low costs and mild reaction conditions. Regioselectively C6-alkylated products were obtained exclusively from tetrahydroquinoline, without the formation of C5-, C7-, C8-, or N-alkylated products.

A route towards the stereocontrolled synthesis of arthrobotrisin A based on a Nozaki–Hiyama–Kishi (NHK) coupling strategy was developed. Highlights of the fragment synthesis include enzyme-catalyzed kinetic resolution, Negishi carbometalation–iodination, quinone formation through oxidation with hypervalent iodine, chiral oxazaborolidine-catalyzed asymmetric Diels–Alder reaction with cyclopentadiene, regio- and stereoselective epoxidation, Noyori reduction, retro-Diels–Alder reaction, diastereoselective Luche reduction, and, finally, a Nozaki–Hiyama–Kishi (NHK) coupling of the vinyl iodide fragment.

An efficient, operationally simple and one-pot multi-component approach has been developed for the construction of pyrazolyl-thiazoles using sulfamic acid (H2NSO3H) as a green catalyst in water. The notable features of this protocol include mild reaction conditions, enhanced selectivity with good yields and wide substrate scope, which makes it an attractive and useful process for the synthesis of biologically important newer pyrazolyl-thiazole compounds. A series of compounds (4a–z) were synthesized and also evaluated for their cytotoxic activity against three human cancer cell lines. Among them, 4b, 4c and 4e exhibited considerable cytotoxicity with an IC50 value of < 5 μM.

The stereochemistry of the drug molecule is gaining greater therapeutic importance and thus much attention was drawn in synthesis of chiral compounds by the pharmaceutical industry. In this study Saccharomyces cerevisiae cells immobilized on functionalized alginate beads, catalyze the bio-reduction of prochiral ketones 1a–12a to their corresponding chiral alcohols 1b–12b in higher yields of 60–99% and.excellent optical purity 75–97%. The synthesized chiral azido alcohols 10b-12b were further subjected to hydrogenation using Palladium(Pd) nanoparticles (≤5 nm), to obtain chiral amino alcohols 10c–12c of therapeutic importance. Thus, a simple, green and inexpensive continuous chemo-enzymatic process has been developed in the synthesis of chiral alcohols/amino alcohols to enhance the scope of the methodology towards industrial application.

A facile and an efficient direct vinylogous aldol/Mannich reaction of furan-2(3H)-one with isatins or isatinimines has been developed by using DABCO as an organocatalyst at room temperature. The synthetic protocol is atom-economical and provides easy access to a variety of oxindole derivatives. This is the first example of a direct vinylogous aldol/Mannich reaction between isatins/isatinimines and furan-2(3H)-one to afford vinylogous aldol adducts. The substrate scope of the protocol is briefly discussed.

A One pot four-component domino reactions were developed for the synthesis of 5-methyl-4-(2-(3-methyl-4-nitroisoxazol-5-yl)-1-arylethyl)-1H-pyrazol-3-ols derivatives in excellent yield from hydrazine hydrate (1), ethyl acetoacetate (2), aldehyde (3) and 3,5-dimethyl-4-nitro-isoxazole (4) using 10 mol% of piperidine. This method is simple, efficient and multiple bonds were generated (two C−C, one C−N, one O−H and one C=N) in a single step. These novel 5-methyl-4-(2-(3-methyl-4-nitroisoxazol-5-yl)-1-arylethyl)-1H-pyrazol-3-ol derivatives are evaluated as anti-bacterial agents.

Rebaudioside-A is the second most abundant sweet diterpene glycoside (1-3%) present in the leaves of Stevia rebaudiana Bertoni, and is now being considered as a possible sucrose substitute due to its pleasant organoleptic properties and associated health benefits. In the present study, a novel in situ enzymatic transglycosylation of stevioside has been developed by pre-treating the stevia leaves with cellulase and adding soluble starch as the glucosyl donor. The results confirm that the transglycosylation of stevioside led to an enrichment in the rebaudioside-A content from 4% to 66%. This was further purified by multiple column chromatography to obtain 95% pure rebaudioside-A. The isolated rebaudioside-A showed concentration-dependent α-glucosidase inhibitory activity with IC50=35.01 μg/ml. Thus the study highlights the biotransformation of stevioside present in stevia leaves to rebaudioside-A by a simple, inexpensive and eco-friendly process that has commercial potential.

A simple, ecofriendly and one-pot three-component aqueous phase protocol is developed for the synthesis of functionalized spirooxindole derivatives by the reaction of isatin, β-nitrostyrene and benzyl amine/α-amino acids in water under microwave irradiation. The method allows the easy construction of a library of spirooxindoles in moderate to good yields with good diastereoselectivity starting from readily available precursors. In addition, all the synthesized compounds were screened for antimicrobial activity and the majority of compounds showed significant activity against Escherichia coli ATCC 10536, Candida tropicalis ATCC 750, Staphylococcus aureus ATCC25923 and Pseudomonas aeruginosa ATCC 15442.

A DABCO catalyzed, novel and efficient one-pot, four component protocol has been developed for the synthesis of (Z)-5-(3-hydroxy-2-oxoindolin-3-yl)-2-iminothiazolidin-4-one scaffolds under metal-free conditions. By virtue of simple and readily available starting materials, mild reaction conditions, and the high bioactivity of oxindole derivatives, this reaction promises diverse applications in medical chemistry.

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.

A novel synthesis of bisheteroarylaryl methanes and triarylmethanes is described by the selective C–C bond cleavage of acetophenones in the presence of SeO2/lanthanide chlorides. The present strategy provides an in situ generation of aldehydes from acetophenones followed by a double Friedel–Crafts reaction of electron-rich arenes. Natural product 1,1,1-tris(3-indolyl)methane is synthesized in a single step following the same protocol.

A simple and an efficient multicomponent domino protocol is developed for the synthesis of 2-iminothiazolines starting from simple and readily available arylacetylenes, amines, and phenyl isothiocyanates under base-free conditions. The present method involves oxy-iodination­ of the arylacetylenes with ammonium iodide and hydrogen peroxide, followed by cyclization processes. A number of diversely functionalized 2-iminothiazolines are synthesized in good to excellent yields.

Stereoselective synthesis of (−)-zeaenol has been accomplished from d -xylose as a chiral pool starting material. The key steps of this convergent synthetic strategy involves a Stille coupling, a Noyori reduction, a Julia–Kocienski olefination and a macrolactonization to obtain (−)-zeaenol. We have also explored a Sonogashira coupling along with a Trost protocol for the intramolecular hydrosilylation on the homopropargylic alcohol system as an alternative synthetic approach to this molecule.

A novel L-proline-catalyzed mild and ecological approach towards the synthesis of 2H-chromene derivatives was achieved by Knoevenagel reaction followed by an intramolecular hemiketalization process. In the present protocol, chemoselectivity has been successfully achieved by using L-proline as catalyst. This eco-friendly and chemoselective reaction provided an alternative synthetic method to prepare previously unknown 2H-chromene derivatives in a one-pot reaction.

Combinatorial libraries of 2-[1-aryl-2-(azaaryl)ethyl]malononitriles derivatives have been synthesized by catalyst-free, one-pot, three-component protocol and employing water as a solvent. Simple reaction, open air reaction, and easy isolation are added advantages of this method. The method is applicable for aryl as well as heteroaryl systems and provides a convenient access for the synthesis of novel quinoline derivatives. All the 2-[1-aryl-2-(azaaryl)ethyl]malononitrile derivatives were evaluated for their antimicrobial activity against Gram-positive bacteria (Staphylococcus aureus, Staphylococcus epidermidis, and Bacillus cereus) and Gram-negative bacteria (Pseudomonas aeruginosa). Eleven compounds exhibited good antibacterial activity against both Gram-positive pathogens and Gram-negative species.

An efficient and general protocol is described for the synthesis of bisindolylmethanes by the reaction of indole with aldehydes in the presence of BF3·OEt2. The method is rapid and applicable for aromatic, heteroaromatic, and aliphatic aldehydes.

The first stereo selective total synthesis of the antimicrobial sesquiterpene trichoderic acid is reported. The key steps of this synthetic strategy involves (R)-CBS-mediated stereoselective keto reduction, Horner–Wadsworth–Emmons (HWE) olefination was employed twice for chain elongation, requisite aldehyde to perform HWE olefination was prepared from commercially available 3-methylcyclohexenone and intramolecular oxa Michael addition.

A simple and an efficient procedure for the formation of diaryl sulfides via direct sp 2 C–H functionalization have been developed from simple and readily available thiophenols and substituted methoxy benzenes. In this process thiophenols were used as the sulfur source. In this transformation broad range of functional groups were well tolerated in good to excellent yields.

An efficient, convenient, and novel one pot approach is described for the synthesis of triarylmethanes by in situ oxidation of benzylalcohols followed by the Friedel–Crafts alkylation of di/trimethoxybenzenes in the presence of BF 3 ·OEt 2 . The generality of the present method is strengthened by screening a variety of aromatic, aliphatic, and heteroaromatic alcohols with methoxy arenes. Shorter reaction time, mild reaction condition, good yields, and wide scope of substrates are the significant features of this protocol.

A facile synthesis of novel functionalized imidazopyridines has been accomplished through the condensation of imidazopyridines with chromene hemiacetals or β-nitro styrenes with high regioselectivity and excellent yields in the presence of a catalytic amount of PTSA or InCl3. In this process, the reaction appears to be very general and suitable for direct functionalization of imidazopyridines. In our present method we successfully achieved regioselectivity.

An expedient, eco-friendly and green-protocol has been developed for the synthesis of novel 4-imino-2-aryl-4H-pyrido[2,1-a]isoquinoline-3-carbonitrile derivatives via Knoevenagel/Michael/cyclisation reactions in one pot under catalyst-free conditions on aqueous media. These products exhibited UV-Vis absorption and photoluminescence properties.

A highly efficient and regioselective β-cross coupling aldol type addition reaction of activated alkenes with isatin/isatinimine derivatives in the presence of Indium/Fe(III) in THF/H2O at room temperature is described. Our synthetic protocol explores a broad substrate scope and smoothly proceeds under base-free conditions. The resulting products are obtained in a short reaction time with moderate to high yields. This is the first example of Mannich-type coupling of isatinimines with activated alkenes to afford the alkyl 3-(2-oxo-3-(phenylamino)indolin-3-yl)propanoates and 3-(3-oxoalkyl)-3-(phenylamino)indolin-2-ones.

An ecofriendly and catalyst free synthesis of novel hybrid molecules of chromene and coumarin is described by C–C bond formation in an aqueous medium under microwave irradiation. The methodology provides cleaner conversion, a shorter reaction time and high regio selectivity which makes the protocol globally recognized. For the first time the reaction between a special type of allylic alcohols 2-hydroxy-2H-chromens and 4-hydroxy coumarin to produce novel functionalised 4H-chromenes in excellent yields was achieved and we evaluated their antibacterial properties.

An efficient synthesis of fused imidazo-heterocycles is described using Cu(OTf)2 in [bmim]BF4 by the multi-component reaction of pyridin-2(1H)-one or thiazol/benzo[d]thiazol-2(3H)-ones with O-tosylhydroxyl amine and acetophenones under microwave irradiation. The present method is very rapid and the product formation occurs via a C–H functionalization/tandem addition-cyclization process. The ionic liquid containing copper triflate is recovered and reused four times.

Stevioside, extracted from the leaves of Stevia rebaudiana Bertoni, is a natural, high intensity, lowcaloric sweetener with wide therapeutic activities. Conventional stevioside extraction methodologies involve the use of non-green solvents, supercritical fluids, microwaves, etc., however, all these processes are expensive, time-consuming and eco-unfriendly. Therefore an alternative process is desired for the isolation of stevioside. In this study, a novel enzyme-mediated extraction (EME) method has been developed. The dry stevia leaves were pre-treated with hydrolytic enzymes aided by transition metal salts (FeCl3). This was followed by pressurized hot water extraction (PHWE) to release stevioside. The crude extract was purified and clarified through multi-stage membrane filtration. The results confirm that metal salt-assisted cellulase pre-treatment enhanced the yield of stevioside to 72%, with 98% purity, which was higher in comparison to existing methods. Thus, the methodology developed establishes a simple, “green”, enzyme-mediated process for the efficient isolation of stevioside under economical and eco-friendly conditions.

A short and facile access to novel functionalized tetrahydroxanthenones via a DABCO-promoted tandem Knoevenagel condensation/hemiketalisation process from easily accessible substrates in a high yield. Tetrahydroxanthenones provide access to the stereo-controlled synthesis of triades or tetrades, which represent privileged structural motifs. Disubstituted tetrahydroxanthenones are generated as a mixture of diastereomers, favoring the formation of selective diastereomers. Unsymmetrical cyclic diketones give mixtures of regio isomers, favoring the formation of sterically less-hindered products.

An I2–DMSO promoted novel and efficient method is described for the synthesis of isatins from 2-aminoaryl methyl ketone. A series of alkyl or aryl isatin derivatives were successfully synthesized under the optimized reaction conditions.

A simple, inexpensive, environmentally friendly, and high yield protocol is described for the synthesis of (5-methylfuran/thiophene-2-yl)isatin by the reaction of 2-methylfuran/2-methylthiophene with isatin/isatin imine in the presence of FeCl3. The present protocol is ideal for the direct introduction of 2-methylfuran/2-methylthiophene onto isatin at 3-position with complete regioselectivity.

A mild and novel approach is described for the synthesis of functionalized fused imidazole analogues in solvent-free and catalyst-free condition in ionic liquid. The short reaction time, good isolated yields, generality and environmentally benign reaction media are the significant features of this protocol.

An I2–DMSO promoted domino protocol was developed for the synthesis of 1,2,2-triarylethanones from readily available aromatic methyl ketones and methoxybenzenes. The 1,2,2-triarylethanones are important precursors for the synthesis of Tamoxifen and Droloxifene. The use of mild reaction conditions, high yield, and single step synthesis are the advantages of the present protocol.

A rapid, efficient, and convenient synthesis of functionalized triarylmethane is described by the Friedel–Crafts alkylation of methoxybenzenes with a variety of aldehydes in the presence of BF 3 ·OEt 2 . The generality of the method is demonstrated by screening a variety of di- or tri-substituted arenes as well as substituted aromatic, heteroaromatic, and aliphatic aldehydes. (−)-Tatarinoid C is synthesized in a single step following the same protocol.

A convenient and efficient method is described for the synthesis of alkoxy substituted 2H-chromens by l -proline catalyzed reaction of salicylaldehydes with diketone in alcohol. The method is applicable for various substituted salicylaldehydes and aliphatic as well as benzylic alcohols.

A highly efficient and green protocol has been developed for the synthesis of 4-(1-aryl-2-nitroethyl)-3-methyl-1H-pyrazol-5-ol via Michael addition of 3-methyl-2-pyrazolin-5-one with β-nitrostyrenes under catalyst free conditions on aqueous medium. A series of 4-(1-aryl-2-nitroethyl)-3-methyl-1H-pyrazol-5-ols have been synthesized with good to excellent yield. C-alkylated product was observed exclusively with 3-methyl-2-pyrazolin-5-one without formation of N-alkylated product.

A one-pot three-component approach for the synthesis of thiazol-2-imines has been described by the reaction of amine, phenyl isothiocyanate and β-nitroacrylate in [Hbim]BF4 ionic liquid. The method is applicable for aromatic, benzylic, aliphatic and cyclic amines. Reusable reaction media, regioselectivity, mild reaction condition, catalyst free and high yield of products are the salient features of this protocol.

A highly efficient method is described for the sp 3 C–H bond functionalization of methyl aza-arenes in the presence of water under microwave irradiation and subsequent addition to aromatic aldehydes. This transformation represents an efficient way to synthesize 2-alkyl aza-arene derivatives from simple starting materials.

An efficient synthesis of 3-hydroxy-3-(alkyl/aryl)indol-2-one derivatives has been described by the reactions of isatin with organoaluminum reagents. The reaction is very rapid and yields are high. The protocol is applicable for substituted isatins as well as a variety of organoaluminums.