Microwave assisted synthesis of indole-annulated dihydropyrano[3,4-c]chromene derivatives via hetero-Diels-Alder reaction

An efficient two-step synthesis of indole-annulated dihydropyrano[3,4-c]chromene derivatives is achieved via Knoevenagel condensation of O-propargylated salicylaldehyde derivatives with indolin-2-ones followed by a microwave-assisted intramolecular-hetero-Diels-Alder reaction of the resulting (Z)-3-(2-(prop-2-ynyloxy)benzylidene)indolin-2-ones in the presence of 20 mol % CuI in acetonitrile.     

Efficient synthesis of novel tricyclic fused pyranothiazolopyrimidine derivatives via isocyanide-based three-component reactions

An efficient and facile one-pot synthesis is described for the preparation of novel tricyclic fused pyranothiazolopyrimidines containing both biologically active thiazolopyrimidine and pyranopyrimidine templates via three-component reaction involving an isocyanide with a dialkylacetylenedicarboxylate (DAAD) and 2,3-dihydro-5H-[1,3]thiazolo[3,2-a]pyrimidine-5,7(6H)-dione, in high yields.     

An efficient multi-component synthesis of (2-amino-3-cyano-4H-chromen-4-yl) phosphonic acid diethyl ester

(2-Amino-3-cyano-4H-chromen-4-yl) phosphonic acid diethyl esters are prepared via a single-step multi-component reaction of structurally diverse salicylaldehydes with malononitrile and triethyl phosphite using a catalytic amount of potassium phosphate in ethanol at ambient temperature. Use of potassium phosphate as an inexpensive catalyst makes the protocol more economical. Mild reaction conditions, simple work-up procedure are the added advantages of the present method.     

Efficient synthesis of diarylidene octahydroacridines by one-pot multi-component tandem reactions

A one-pot multi-component reaction is developed for the efficient synthesis of 4,5-dibenzylidene octahydroacridines in high yields. The reaction is performed by the tandem reaction of three molar equivalent aromatic aldehydes with two molar equivalent 4-alkylcyclohexanone in the system of NH₄OAc/HOAc under microwave irradiation.      

Iodine catalyzed synthesis of the chromene derivatives in one-pot

Iodine catalyzed one-pot reactions of salicylaldehyde and dimolecular 1 H-indene-1,3(2H)-dione,barbituric acids,4-hydroxycoumarin, or 4-hydroxy-6-methylpyran-2-one were performed and provided a rapid,convenient and general approach to synthesize the chromene derivatives.2-(11-Oxo-10,11-dihydroindeno[l,2-b]chromen-10-yl)-1H-indene-1,3(2H)-diones P1-P4 and 10-(4-hydroxy-6-methyl-2-oxo-2H-pyran-3-yl)-3-methylpyrano[4,3-6]chromen-1(10H)-ones P8-P9 were unprecedentedly prepared and structurally identified by NMR and Mass.The confirmation of structure by single crystal X-ray crystallography is reported for P3.     

Design,synthesis, characterization,and antimicrobial evaluation of some new pyridine and chromene derivatives containing Lidocaine analogue

In an attempt to find a new class of antimicrobial agents, a series 2-pyridinone and 2-iminochromene derivatives containing Lidocaine analogue were designed and synthesized. The 2-pyridinone derivatives (3), (4), and (6) were obtained through the cyclocondensation of 2-cyano-N-(2,6-dimethylphenyl)-acetamide (2) with 1,3-dicarbonyl compounds and/or ternary condensation of (2), aromatic aldehyde, and malononitrile. Also, a series of 2-iminochromene derivatives (7–9) were synthesized through the condensation reaction of cyanoacetamide derivative (2) with salicylaldehyde derivatives. The structure of the new compounds were confirmed based on elemental analysis and spectral data. These compounds were screened for their antibacterial and antifungal activity The minimal inhibitory concentration (MIC) (µg/mL) of the most active (4), (5b), and (8) derivatives were determined. The MIC values between 7.81 and 31.26 µg/mL against bacterial species for (8) derivative, and upon comparison to tetracycline exhibited a positive control MIC (31.26–62.6 µg/mL). Besides, the activity against C. albicans (ATCC 1023) showed a MIC value of 15.63 µg/mL, which is similar to that of Amphotericin B.     

Bakers’ yeast catalyzed synthesis of polyhydroquinoline derivatives via an unsymmetrical Hantzsch reaction

Bakers’ yeast efficiently catalyzes the unsymmetrical Hantzsch reaction through a four-component coupling of aldehydes, β-ketoesters, dimedone and ammonium acetate to form polyhydroquinoline derivatives in good to excellent yields.     

Enantioselective organocatalytic synthesis of medicinally privileged 2-amino-4H-chromene-3-carbonitriles via a cascade process

An efficient organocatalytic cascade approach toward medicinally privileged 2-amino-4H-chromene-3-carbonitriles is reported. The enantioselective synthesis of these compounds is achieved in high yields and good to high ee values (up to 96% yield and 89% ee) using bifunctional amine-thiourea organocatalysts developed in our laboratory.     

DABCO promoted one-pot synthesis of dihydropyrano(c)chromene and pyrano[2,3-d]pyrimidine derivatives and their biological activities

A simple and efficient one-pot synthesis of heteroaryl substititued dihydropyrano(c)chromenes and pyrano[2,3-d]pyrimidines has been developed via initial Knoevenagel, subsequent Micheal and final heterocyclization reactions of heteroaryl aldehyde, malononitrile and barbituric acid/ dimedone. 1,4-Diazabicyclo [2.2.2] octane (DABCO) has been used as a catalyst. Short reaction time, environment friendly procedure and excellent yields are the main advantages of this procedure. All synthesized compounds have shown good antimicrobial activity against different microbial stains.     

Oxymethylcrowned chromene: photoswitchable stoichiometry of metal ion complex and ion-responsive photochromism

Chromene derivatives bearing oxymethyl-12-crown-4 (1), -15-crown-5 (2), -18-crown-6 (3) ether moieties, and non-cyclic analogue (4) were synthesized, and their metal ion binding properties and photochromism were examined. NMR titration with alkali metal ions revealed that 1 formed a 1:2 complex (metal ion: ligand) with Na⁺, while Li⁺ afforded a 1:1 complex of 1. In cases of K⁺ and Rb⁺, the complexes were a mixture of 1:1 and 1:2 complexes, but the formation of 1:1 complex was observed again with Cs⁺. Under UV irradiation, however, the complex stoichiometry of 1 with all alkali metal ions was 1:1. As a comparison of NMR spectra between the Li⁺ and Na⁺ complexes of 1 indicated considerable upfield shift for the chromene moiety of the Na⁺ complex, π-π stacking of the chromene moiety seems to induce formation of the 1:2 complex. These results indicate that the chromene moiety is not only to show photochromism but also to induce aggregation to form the 1:2 complex resulted in switching of the complex stoichiometry by UV irradiation. The formation of 1:2 complex appeared only with 1 because flexibility of the crown moieties for 2 and 3 interfered the formation of 1:2 complex. Studies on photochromism in the presence of a metal ion demonstrated that the chromene derivatives bearing crown ether moieties show ion-responsive photochromism depending on the metal ion binding ability of their crown ether moieties.     

Electrocatalytic one pot synthesis of medicinally relevant 4H-benzo[g]chromene and pyrano[2,3-g]chromene scaffold via multicomponent-domino approach

A highly efficient one pot, multicomponent synthesis of 4H-benzo[g]chromene and pyrano[2,3-g]chromene derivatives are reported by electrochemically stimulated condensation of an aromatic aldehyde, malononitrile and some enolizable acidic compounds in ethanol at room temperature under constant current density. By utilizing common electrode materials and a simple constant current protocol, this method is a new alternative to conventional methods.     

A facile and expeditious microwave-assisted synthesis of 4-aryl-2-ferrocenyl-quinoline derivatives via multi-component reaction

An efficient and rapid route for the synthesis of 4-aryl-2-ferrocenyl-quinoline derivatives through microwave-assisted multi-component reaction of acetylferrocene with aromatic aldehyde and dimedone in the presence of ammonium acetate using DMF as reaction media at 100 °C is described. This novel procedure lends itself well to combinatorial methods, providing the target heteropolymetallic compounds in excellent yield without further purification.     

A facile and rapid route for the synthesis of novel 1,5-substituted tetrazole hydantoins and thiohydantoins via a TMSN3-Ugi/RNCX cyclization

This Letter describes novel methodology for the rapid assembly of new and biologically appealing 1,5-substituted tetrazole-hydantoins and thiohydantoins. The product of a TMSN₃-Ugi multi-component reaction is treated with an excess of isocyanate or isothiocyanate to generate the final scaffold in moderate to good yields. The applicability of this solution phase methodology to the preparation of a small collection of compounds is discussed.     

Microwave promoted diastereoselective synthesis of dihydroindeno[1,2-b]furans via one-pot three-component reaction in solvent-free conditions

An efficient method was developed for the synthesis of fused dihydroindeno[1,2-b]furans. One-pot three-component reaction of 1,3-indanedione, aromatic aldehyde and pyridinium ylide in the presence of triethylamine under microwave-irradiation in solvent-free conditions afforded dihydroindeno[1,2-b]furans in a diastereoselective manner in excellent yields.     

Efficient synthesis of isoflavone analogues via a Suzuki coupling reaction

Analogues of 3-aryl-8-isobutyl-5,6,7-trihydroxy-2-methyl-4H-chromen-4-one were synthesized with high yields via the Suzuki coupling reaction of 3-iodo-8-isobutyl-5,6,7-trimethoxy-2-methyl-4H-chromen-4-one with different aryl boronic acids.     

Copper-doped silica cuprous sulfate: A highly efficient heterogeneous nano-catalyst for one-pot three-component synthesis of 1-H-2-substituted benzimidazoles from 2-bromoanilines,aldehydes, and [bmim]N3

A facile and highly efficient one-pot three-component synthesis of 1-H-2-substituted benzimidazole derivatives from readily available substrates catalyzed by copper-doped silica cuprous sulfate (CDSCS) is described. In this method, treatment of diverse 2-bromoanilines, aldehydes, and [bmim]N₃ in DMF at 110 °C in the presence of CDSCS as a highly efficient heterogeneous nano-catalyst affords the corresponding 1-H-2-substituted benzimidazoles in good to excellent yields. The CDSCS is an inexpensive and stable nano-catalyst that could be simply prepared, recovered and reused for many consecutive reaction runs without significant loss of its activity.     

A pseudo multi-component electrochemical synthesis of spiro dihydrofuran derivatives

An electrochemical strategy to the assembly of tricyclic spiro dihydrofuran scaffold via the reaction of aryl aldehyde and dimedone has been developed successfully. This protocol has the advantages of high yields, wide application scope and an environmental benign procedure compared with the reported methods.     

Development of an unexpected reaction pathway for the synthesis of 1,2,4-trisubstituted pyrrolo[1,2-a]quinoxalines through palladium-catalyzed cascade reactions

1,2,4-trisubstituted pyrrolo[1,2-a]quinoxalines are synthesized through the multi-component reaction of 3-substituted 2-chloroquinoxalines, propargyl bromide, and excess secondary amines in the presence of a palladium copper catalytic system. This one-pot process provides an unexpected synthesis of new trisubstituted pyrrolo[1,2-a]quinoxalines by the introduction of two amine substituents onto the fused pyrrole rings in a single reaction procedure. The compounds formed are fully characterized by the analytical spectral data and X-ray analysis. A number of synthesized pyrrolo[1,2-a]quinoxaline derivatives are also screened against the three bacterial strains Micrococcus luteus, Pseudomonas aeruginos, and Bacillus subtilis. According to the results obtained, compounds 3b, 3c, and 3e are active against M. luteus, compounds 3b and 3e are active against Ps. Aeruginos, and only compound 3f is active against all the three bacterial strains.     

Iodine-promoted three-component reaction for the synthesis of spirooxindoles

An iodine-promoted three-component reaction for the construction of spirooxindoles has been developed through the green reaction system of catalytic amount of molecular iodine as an alternative catalyst for Lewis acids. Various substituted isatins were able to react with different cyclic 1,3-dicarbonyls and 4-hydroxyl coumarins through this reaction strategy, which shows good functional group tolerance and efficiency.