Search

The synthesis of fused dihydropyridines was accomplished for the first time using PPh3–NBS via a formal [3 + 2 + 1] cycloaddition of 1,3-bisnucleophiles, β-enaminones and aldehydes in aqueous medium.

A novel protocol to synthetic transformation of 4H-chromenes into dihydrofurans (3) and 2H-chromenes (11) promoted by hypervalent iodine has been accomplished in a one-pot reaction at ambient tempe...

The title compounds were synthesized from 5,5-dimethyl­cyclohexane-1,3-dione, benzaldehyde, and malononitrile promoted by molecular iodine in basic medium via 2-amino-7,7-dimethyl-5-oxo-4-phenyl-5,6,7,8-tetrahydro-4H-chromene-3-carbonitrile, by a novel protocol. The protocol involves a novel rearrangement in which the 4H-chromene fragment dissociates to a cyclopropane moiety and rearranges to the five-membered compound 6,6-dimethyl-4-oxo-2-phenyl-4,5,6,7-tetrahydrobenzofuran-3,3(2H)-dicarbonitrile. Simple reaction conditions, excellent yields, and high compatibility are the advantages of this protocol.

Reduction of various azides using Na2S has been accomplished in water, and, in situ, the resulting amines on reaction with various ketones lead to pyrazolo[3,4-b]pyridines in one pot. Thus, a number of new trifluoromethyl-substituted pyrazolo[3,4-b]pyridine compounds have been prepared and screened for antimicrobial activity against different Gram-positive and Gram-negative strains. A good number of compounds, 4a, 4b, 4d, 4f, 4i, 4k, 4l, 4m, 4r and 4s, were found to possess promising activity. Notably, Na2S on hydrolysis in water generates H2S and NaOH, which facilitate the reduction of azides followed by intramolecular cyclization leading to the title compounds. To the best of our knowledge, this is the first report of the synthesis of the title compounds in aqueous medium in a one-pot reaction.

A simple and straightforward protocol has been accomplished for synthesis of pyrazolo[3,4-b]pyridines by reacting 5-amino-1-phenyl-3-(trifluoromethyl)-1H-pyrazole-4-carbaldehyde (1) and β-enaminoketones (2) promoted by Iron(III)chloride. This protocol was also able to produce quinolines (5) by the reaction of O-nitrobenzaldehydes and β-enaminoketones. Simple reaction conditions, high compatibility and excellent yields are the advantages of this protocol.

A simple, green protocol has been accomplished for the synthesis of dihydrospirofuro[2,3-c]pyrazoles in aqueous medium involving pyrazolone and aldehydes in a one-pot reaction promoted by bis(acetoxy)iodobenzene (BAIB) at ambient temperature. The protocol presented herein describes a new transformation where two molecules of pyrazolone react with an aldehyde in a Knoevenagel condensation followed by a Michael addition, and the resulting dienol was rearranged to the title compound. High compatibility, easy work-up, and excellent yields are the advantages of this protocol.

Synthesis of a series of tricyclic quinazolinones have been accomplished starting from anthranilamide and 1,3-cyclic dione promoted by TsOH·H2O The protocol presented herein based on retro-Dieckmann type reaction, leading to incorporation of dione as an acyclic unit into the product. Simple reaction conditions, broad scope, excellent yields are the advantages of this protocol. Further, this methodology is extended to the synthesis of pyridopyrimidinones and benzimidazopyridines.

Reduction of various azides using Na2S has been accomplished in water, and, in situ, the resulting amines on reaction with various ketones lead to pyrazolo[3,4-b]pyridines in one pot. Thus, a number of new trifluoromethyl-substituted pyrazolo[3,4-b]pyridine compounds have been prepared and screened for antimicrobial activity against different Gram-positive and Gram-negative strains. A good number of compounds, 4a, 4b, 4d, 4f, 4i, 4k, 4l, 4m, 4r and 4s, were found to possess promising activity. Notably, Na2S on hydrolysis in water generates H2S and NaOH, which facilitate the reduction of azides followed by intramolecular cyclization leading to the title compounds. To the best of our knowledge, this is the first report of the synthesis of the title compounds in aqueous medium in a one-pot reaction.

The synthesis of a series of novel quinoline fused imidazo[4,5-c]quinolines was accomplished by a simple, efficient, iodine–dimethyl­ sulfoxide (I2–DMSO) promoted sequential oxidative cross coupling­ followed by intramolecular cyclization of pyridoimidazole arylamines and carbonyl compounds in a one-pot reaction. Simple reaction conditions, no metal catalyst, no additives, no ligand, selective product formation and high yields are the advantages of this method.

Synthesis of a number of 2-cyano-4-oxo-3-phenyl-3,4-dihydro-2H-furo[3,2-c]chromene-2-carboxylate compounds (5) have been accomplished by a simple, multicomponent one pot reaction and evaluated for in vitro antimicrobial activity against different Gram-positive and Gram-negative bacterial strains. The outcome of the screening study showed that compound 5c exhibited promising activity against Micrococcus luteus MTCC 2470 and Klebsiella planticola MTCC 530. Whereas, compound 5g exhibited excellent activity against Bacillus subtilis MTCC 121, Micrococcus luteus MTCC 2470, Klebsiella planticola MTCC 530, Escherichia coli MTCC 739 and displayed a moderate activity against Staphylococcus aureus MTCC 96 and Candida albicans MTCC 3017 when compared with Ciprofloxacin (standard control).

A number of 3-hydroxy-6-(hydroxymethyl)-2-(2-phenyl-4H-chromen-4-yl)-4H-pyran-4-ones (3) have been synthesized in a one pot catalyst free reaction of 2-hydroxy chalcone (1) with kojic acid (2) in toluene at reflux temperature and evaluated for antimicrobial and anti-biofilm activities. Compounds 3a, 3e, 3f, 3l showed potent antimicrobial activity against Staphylococcus aureus MLS-16 MTCC 2940, Bacillus subtilis MTCC 121 and Escherichia coli MTCC 739, whereas 3b and 3k exhibited excellent activity against Bacillus subtilis MTCC 121 and Escherichia coli MTCC 739, while 3g showed promising activity against Bacillus subtilis MTCC 121 and Escherichia coli MTCC 739. On the other hand, compounds 3a, 3b and 3l showed very good anti-biofilm activity and 3g showed moderate activity against Bacillus subtilis MTCC 121. Whereas, compounds 3a and 3f showed moderate activity against Escherichia coli MTCC 739, while compounds 3a, 3b, 3k and 3l displayed similar activity against Staphylococcus aureus MLS-16 MTCC 2940.

A simple, highly efficient and selective oxidative cross coupling of imidazo[1,2-a]pyridine (IP) compounds (1) and methylketones (2), promoted by molecular iodine in DMSO in the presence of a catalytic amount of PTSA has been realized in a one pot reaction. This strategy has provided a general route for the synthesis of 1-aryl-2-(2-phenylimidazo[1,2-a]pyridin-3-yl)ethane-1,2-diones (3) with a new C–C bond formation through Kornblum oxidation followed by nucleophilic attack of IP compounds (1) on the in situ formed phenylglyoxal. Simple reaction conditions, no metal catalysts and selective product formation are the advantages of this protocol.

A one-pot access to cyclic 1,3-dione fused symmetrical 2,8-dioxabicyclo[3.3.1]nonanes (4) via acetic acid-mediated reaction of β-enamino ketones (1) and 1,3-cyclohexanediones (2) by heating under reflux is reported. The reaction proceeds via intramolecular cyclization of intermediate 2,2′-(3-oxo-3-arylpropane-1,1-diyl)bis(3-hydroxy-5,5-dimethylcyclohex-2-en-1-one) (3) and is highly selective towards the formation of product 4. Unlike similar reactions, the presence of trifluoroacetic acid in a toluene medium affords xanthenes (5) exclusively.

A simple and efficient one pot protocol is accomplished to access tricyclic spiro dihydrofurans (4) by the reaction of β-enamino ketones (1) and dimedone (2) in ethanol followed by sequential addition of N-chloro succinimide (NCS) at ambient temperature for the first time. The Selectivity in desired product formation in good yields is the advantage of this protocol.

The stereoselective total synthesis of epi-phomopsolide B, a polyhydroxy lactone natural product, has been accomplished. Starting from the commercially available diethyl l -tartrate, the synthesis­ involved an asymmetric Evans aldol approach and Still–Gennari olefination. Further, the resulting epi-phomopsolide B was screened for cytotoxicity and antimicrobial properties, and the outcome is presented.

Regioselective synthesis of a number of highly functionalized 3-benzylpyrimidino chromen-2-ones (4) were accomplished in a one pot three component reaction in acetic acid and determined their anti-microbial and anti-biofilm activities. Compounds 4o and 4p showed an excellent anti-microbial activity against Micrococcus luteus MTCC 2470 at a par with standard control (Ciprofloxacin) and exhibited best activity against Staphylococcus aureus MTCC 96 and Bacillus subtilis MTCC 121. Further, compounds 4h, 4i, 4m, 4n and 4q showed promising activity against Micrococcus luteus MTCC 2470, Staphylococcus aureus MTCC 96 and Bacillus subtilis MTCC 121. Whereas, compounds 4m showed very promising biofilm inhibition activity against Staphylococcus aureus MLS 16 MTCC 2940 and 4o, 4p showed very potent activity against Staphylococcus aureus MTCC 96 at a par with Ciprofloxacin used as standard control.

Synthesis of a series of novel aryl and heteroaryl fused 2,8-dioxabicyclo[3.3.1]nonanes (3) was accomplished by one pot, catalyst free reaction of 2-hydroxy chalcone (1) with 3-trifluoromethyl substituted pyrazolone (2) in xylene at reflux temperature. The role of the trifluoromethyl functional group in formation of 3 was confirmed by comparative studies with 3-methyl substituted pyrazolones (2c,d) and the outcome is presented.

A series of novel fluorinated 11H-azaindolo[3,2-c]isoquinolines (7) have been synthesized starting from 2(1H)pyridones (1) via azaindoles (5). Initially, compound 1 was treated with POCl3/DMF, and the resulting compound 2 was reacted with benzylamine to obtain compounds 3 that were subjected to cyclization after protecting the secondary amine to get azaindoles (5). Further, compounds 5 were subjected to cyclization as per Pictet–Spengler reaction condition. However, it was not successful. Subsequently, the azaindoles (5) were acetylated and then cyclized to give title compounds 7. These compounds are new and well characterized by spectral data.

A one-pot access to cyclic 1,3-dione fused symmetrical 2,8-dioxabicyclo[3.3.1]nonanes (4) via acetic acid-mediated reaction of β-enamino ketones (1) and 1,3-cyclohexanediones (2) by heating under reflux is reported. The reaction proceeds via intramolecular cyclization of intermediate 2,2′-(3-oxo-3-arylpropane-1,1-diyl)bis(3-hydroxy-5,5-dimethylcyclohex-2-en-1-one) (3) and is highly selective towards the formation of product 4. Unlike similar reactions, the presence of trifluoroacetic acid in a toluene medium affords xanthenes (5) exclusively.

The simple, efficient and one-pot, catalyst-free protocol leads to the synthesis of new 2-sulfenylimine chromene compounds.

A series of fluorinated tetrahydropyrano[3,2-c]chromenes and dihydropyrano[3,2-b]pyran derivatives have been synthesized and their in vitro cytotoxic activities have been determined in cervical cancer cell line (HeLa), human breast adenocarcinoma cell line (MDA-MB-231 and MCF-7) and human alveolar adenocarcinoma cell line (A549). Compounds 4g, 4k, 4p showed a very potent activity against MDA-MB-231, and 4c, 4p showed promising activity against MCF-7, while compounds 4c, 4g, 4p showed moderate activity against HeLa.

The synthesis of 2-sulfenylimine chromene compounds (8) is accomplished by reacting benzaldehyde (1), malanonitrile (2) and dimedone (3) followed by sequential addition of N-chlorosuccinimide and thiophenols to the in situ formed 2-amino-4(H) chromenes (4) in a one pot, catalyst free, five component reaction in toluene medium. When aniline was employed as the nucleophile in place of thiophenol, the formation of hexahydrobenzofuran-2-N-phenyl carboxamide derivatives (5) was observed. Excellent yields, simple reaction conditions and high compatibility are the advantages of this protocol.

Various of the novel title compounds (III) (16 examples) display potent antimicrobial activities, e.g. (IIIa-c), (IIIg), (IIIi), as well as very good anti-biofilm activity.

Various aryl(phenylimidazo[1,2-a]pyridinyl)ethanediones are selectively obtained with a new C—C bond formation via Kornblum oxidation followed by nucleophilic attack of a imidazo[1,2-a]pyridine on the in situ generated phenylglyoxal.

The title compound (I) shows cytotoxic activity against HeLa, A549, DU145 and HepG2 cell lines and antimicrobial activity against Staphylococcus aureus MLS-16 MTCC 2940 and Bacillus subtilis MTCC 121.

A library of novel 3-trifluoromethyl pyrazolo-1,2,3-triazole hybrids (5-7) were accomplished starting from 5-phenyl-3-(trifluoromethyl)-1H-pyrazol-4-amine (1) via key intermediate 2-azido-N-(5-phenyl-3-(trifluoromethyl)-1H-pyrazol-4-yl)acetamide (3) through click chemistry approach. Thus obtained compounds in 5-7 series were evaluated for in vitro antimycobacterial activity against Mycobacterium smegmatis (MC(2) 155) and also verified the cytotoxicity. These studies engendered promising lead compounds 5q, 7b and 7c with MIC (μg/mL) values 15.34, 16.18 and 16.60, respectively. Amongst these three compounds, 2-(4-(4-methoxybenzoyl)-1H-1,2,3-triazol-1-yl)-N-(5-phenyl-3-(trifluoromethyl)-1H-pyrazol-4-yl) acetamide (5q) emerged as the most promising antitubercular agent with lowest cytotoxicity against the A549 cancer cell line. This is the first report to demonstrate the pyrazolo triazole hybrids as potential antimycobacterial agents.

For the first time, a simple, efficient, and catalyst free protocol to synthesize a series of novel 3-trifluoromethyl substituted title compounds is developed.

A mild and efficient method for the functionalization of chromen-2-ones with amidoalkyl derivatives have been developed starting from 4-trifluoromethyl substituted chromen-2-ones, aromatic aldehydes and acetamide promoted by stannous chloride dihydrate in a one pot three component reaction under solvent free condition. Simple reaction conditions, high yields and environmentally benign procedure are the advantage of this protocol.

The reaction of chromene derivatives (I) with NCS affords dihydrofurans (III) after an unusual rearrangement in good yields.

Quinoxalines are omnipresent heterocyclic structural units in pharmaceuticals and bioactive natural products. They have been widely used in dyes 1 , electrical/photochemical materials 2,3 . They are the core constituents of the various antibiotics such as Echinomycin, Levomycin and Actinoleutin 4,5 As a result quinoxalines have attracted considerable interest from chemists. Water is the most preferred solvent for chemical reactions. Its use gained momentum in spite of limited usage in organic reactions as organic substrates have poor solubility and greater sensitivity to it. Yet water is the desirable solvent for organic reactions owing to cost, safety, non-toxicity and environmental concerns 6-11 . Surfactants 12-14 are successfully used in water mediated organic reactions as they considerably improve the solubility of organic substrates and also act as catalysts in promoting the reaction by way of aggregation in water to form micelles with hydrophobic core and hydrophilic corona at ambient temperatures. The uses of micellear surfactants as catalysts is widespread and have been investigated in detail in various water mediated organic reactions. Several methods are well documented in the literature on the synthesis of quinoxalines. A traditional method for this synthesis involves the reaction of benzene 1,2-diamines with 1,2-dicarbonyl compounds 15-19 with or without the presence of catalyst and also on solid support. Other methods include the reaction of 1,2-diaza-1,3-butadiens with 1,2-diamines 20 , oxidation trapping of α-hydroxyketones with 1,2-diamines 21,22 and reaction of phenacyl bromide with phenyl 1,2-diamines using catalysts such as β-cyclodextrin (β-CD) (Ref 23), HClO4-SiO2 (Ref 24) and 1,4-diazabicyclo[2.2.2]octane (DABCO) (Ref 25).

A variety of highly functionalized pyrimidinylmethylchromene derivatives (IV) (22 examples) are synthesized via a one-pot three-component reaction.

A series of novel fluorinated 11H-azaindolo[3,2-c]isoquinolines (7) have been synthesized starting from 2(1H)pyridones (1) via azaindoles (5). Initially, compound 1 was treated with POCl3/DMF, and the resulting compound 2 was reacted with benzylamine to obtain compounds 3 that were subjected to cyclization after protecting the secondary amine to get azaindoles (5). Further, compounds 5 were subjected to cyclization as per Pictet–Spengler reaction condition. However, it was not successful. Subsequently, the azaindoles (5) were acetylated and then cyclized to give title compounds 7. These compounds are new and well characterized by spectral data.

Hitherto unreported fluorinated pyranochromene (IV) and pyranopyran derivatives (VI) are synthesized via simple multicomponent reactions and evaluated for their cytotoxicity against a panel of human tumor cell lines.

We performed a structure-activity relationship (SAR) study of a novel aspirin (ASA) derivative, which shows strong anticancer activity in vitro and in vivo. A series of ASA-based benzyl esters (ABEs) were synthesized and their inhibitory activity against human colon (HT-29 and SW480) and pancreatic (BxPC-3 and MIA PaCa-2) cancer cell lines was evaluated. The ABEs that we studied largely comprise organic benzyl esters bearing an ASA or acyloxy group (X) at the meta or para position of the benzyl ring and one of four different leaving groups. The nature of the salicyloyl/acyloxy function, the leaving group, and the additional substituents affecting the electron density of the benzyl ring, all were influential determinants of the inhibitory activity on cancer cell growth for each ABE. Positional isomerism also played a significant role in this effect. The mechanism of action of these compounds appears consistent with the notion that they generate either a quinone methide or an m-oxybenzyl zwitterion (or an m-hydroxybenzyl cation), which then reacts with a nucleophile, mediating their biological effect. Our SAR study provides an insight into the biological properties of this novel class of compounds and underscores their potential as anticancer agents.

A simple, catalyst free, water mediated, one pot four component, green protocol was developed for title compounds 7 starting from aromatic aldehydes (1), malononitrile (2), 1,3-diones (3) and N-chlorosuccinimide (NCS) in a sequential addition reaction at ambient temperature. The approach presented herein, for the first time, is through an unusual rearrangement where NCS was reacted with 2-amino-7,7-dimethyl-5-oxo-4-aryl-5,6,7,8-tetrahydro-4H-chromene-3-carbonitrile (4), which was formed by the Knoevenagel condensation of aldehyde and malononitrile followed by the Michael addition of 3. In addition, this novel protocol is compatible with various aldehydes and active C–H functional derivatives, accomplishes high yields and follows the GAP chemistry principle. Interestingly, compound 4 when reacted with NCS in alcohol medium gave 2-cyano-6,6-dimethyl-4-oxo-3-aryl-2,3,4,5,6,7-hexahydrobenzofuran-2-carboxylate (5).

A mild and efficient method for the functionalization of chromen-2-ones with amidoalkyl derivatives have been developed starting from 4-trifluoromethyl substituted chromen-2-ones, aromatic aldehydes and acetamide promoted by stannous chloride dihydrate in a one pot three component reaction under solvent free condition. Simple reaction conditions, high yields and environmentally benign procedure are the advantage of this protocol.