Synthesis of fused pyran and arylbis(4-hydroxy-6-methyl-2-oxo-2H-pyran-3-yl)methane in ionic liquid

Promoted and mediated by an ionic liquid-[bmim][BF4], fused pyrans or arylbis（4-hydroxy-6-methyl-2-oxo-2H-pyran-3- yl）methanes were efficiently and selectively prepared from the reaction of aldehyde and 4-hydroxy-6-methyl-2-oxo-pyran with or without acetic anhydride. By using these novel procedures, pyrimidine nucleoside-fused pyran and arylbis（pyranon-3-yl）methane hybrids with potential biological activities were constructed.

Palladium (0) Nanoparticles: A Novel and Reusable Catalyst for the Synthesis of Various Pyran Derivatives

A ligand free, Palladium nanoparticles catalyzed synthesis of pyran derivatives using C-H activated compound, malononitrile and aryl aldehyde via Knoevenagel condensation followed by Michael addition reaction using Palladium nanoparticles as catalyst in one-pot is described herein. The advantages of this method lie in its simplicity, low catalyst loading, cost effectiveness and easy to handle. The Palladium Nanoparticles can be reused without loss of activity even after recycling four times. The palladium nanoparticles were characterized by powder X-ray diffraction (XRD), transmission electron microscopy (TEM). The present method also allows us to synthesize highly functionalized title compounds from simple and readily available inputs.

Synthesis, Crystal Structure and Properties of Ethyl 3,9-Dimethyl-7-phenyl-6H-dibenzo[b,d]pyran-6-one-8-carboxylate

ABSTRACT Ethyl 3,9-dimethyl-7-phenyl-6It-dibenzo[b,d]pyran-6-one-8-carboxylate （C24H20O4, Mr = 372.40） has been synthesized and its structure was determined by ^1H and ^1C NMR, ESI-MS, elemental analysis, and X-ray single-crystal diffraction. The crystal belongs to the monoclinic system, space group P21/n, with a = 8.3674（11）, b = 10.6683（14）, c = 11.3817（15） A, a = 95.596（2）, β = 109.866（2）, γ = 94.495（2）°, V= 944.2（2）A^3, Z= 2, Dc = 1.310 g/cm3, μ= 0.089 mm^-1, F（000） = 392, R = 0.0482 and wR = 0.1281 for 2916 observed reflections with I 〉 2σ（I）. In the crystal structure, the fused tricyclic nucleus of the title compound is not fully coplanar. Analysis of the crystal packing indicates aromatic π-π stacking interactions occurring between the fused tricyclic aromatic rings of neighboring molecules in which a maximum overlap of the x-electron systems was achieved. Fluorescence and thermal studies indicate that compound 3 has good optical properties and thermal stability.

<i>β</i>-Oxoanilides in Heterocyclic Synthesis: Synthesis and Antimicrobial Activity of Pyridines, Pyrans, Pyrimidines and Azolo, Azinopyrimidines Incorporating Antipyrine Moiety

Condensation of β-Oxoanilide 1 with active methylene derivatives 2a,bafforded the pyridine derivative 5, and with crotononitrile afforded the pyridine 8. Compounds 9 and 11a-c were obtained by reaction of 1 with malononitrile dimer and arylidinemalononitrile 10a-10c. In contrast, when compound 1 reacted with ethoxymethylen malononitrile afforded the pyridine derivative 13. On the other hand, treatment of 1 with anthranilic acid gave the quinoline derivative 14. Also, reactions of 1 with isothiocyanate derivatives afforded compounds 16-18. The reaction of 1 with chalcone derivative afforded the pyridine derivative 22. Treatment of compound 1 with thiourea produced pyrimidine derivative 23. Furthermore, compound 1 converted into pyrimidinethione 24a and pyrimidinone 24b on treatment with a mixture of aromatic aldehydes and thiourea or urea respectively. Reaction of 24a with hydrazonyl halide, thiosemicarbazide and arylidinecyanothioacetamide afforded compounds 26, 28 and 29. Compound 29 was treated with chloroacetonitrile to afford compound 30. Six compounds from the newly synthesized were screened for antibacterial and antifungal activity against bacteria staphylococcus aureus, bacillus cereus and klebsiella pneumonia and fungi aspergillus flavus and aspergillus ochraceous, respectively. Some of the tested compounds showed significant antimicrobial activity. IR, 1H NMR, mass spectral data, and elemental analysis elucidated the structures of all the newly synthesized compounds.

Crystal Structure and Antiproliferative Activity of Ethyl 3,9-Dihydroxy-9-methyl-7-phenyl-7,8,10-trihydro-6Hdibenzo[b,d]pyran-6-one-8-carboxylate

Ethyl 3,9-dihydroxy-9-methyl-7-phenyl-7,8,10-trihydro-6H-dibenzo[b,d]pyran-6-one-8-carboxylate（C（23）H（22）O6,Mr = 394.42） has been synthesized and its structure was determined by ~1H and ^（13）C NMR,ESI-MS,elemental analysis,and X-ray single-crystal diffraction.The crystal belongs to the triclinic system,space group P1,with a = 8.8220（17）,b = 9.881（2）,c = 12.157（2） A,α= 90.488（3）,β= 102.664（4）,γ= 98.799（3）°,V= 1020.8（3） A^3,Z= 2,Dc = 1.342 g/cm^3,μ= 0.099mm^（-1）,F（000） = 436,R = 0.0615 and wR = 0.2501 for 2592 observed reflections with（I2σ（I））.In the crystal structure,the coumarin ring system is planar and the 3：4 fused cyclohexane ring adopts distorted half-chair conformation.Rich hydrogen bonding interactions are formed between compound 2 and lattice water molecules.These interactions assemble molecules of 2 into 2D layered networks in an AB stacking sequence.Its in vitro antiproliferative activities against three human cancer cell lines were evaluated by MTT assay.

Crystal Structure of 2-Amino-5,10-dioxo-4-aryl-5,10-dihydro-4H-naphtho [2,3-b]pyran-3-carboxylic Acid Ethyl Ester

The title compounds have been synthesized via a three-component reaction and their structures were characterized by IR, ^1H NMR, ^13C NMR and X-ray single-crystal diffraction. The crystal of compound 4a belongs to monoclinic, space group P121/c1 with a = 8.575（3）, b = 9.590（3）, c = 21.431（6）A, β = 91.172（3）°, V = 1762.1（9）A^3, Mr = 393.36, Z = 4, Dc= 1.483 g/cm^3, μ（MoKα） = 0.113 mm^-1, F（000） = 816, the final R = 0.0366 and wR = 0.0941. The crystal of compound 4b is of triclinic, space group P-1 with a = 8.6420（17）, b = 9.761（2）, c = 11.132（2） A, α = 97.51（3）, β = 97.86（3）, γ = 92.85（3）°, V = 920.1（3） A^3, Mr = 393.36, Z = 2, Dc = 1.420 g/cm^3, μ（MoKα） = 0.108 mm^-1, F（000） = 408, the final R = 0.0612 and wR = 0.1781. In each molecular structure, the naphthalene rings and pyran rings are almost coplanar with the latter in an envelope conformation. The rings formed by the N-H…O intramolecular hydrogen bonds are almost planar in these compounds. Their crystal packing is stabilized by intermolecular hydrogen bonds together with C-H…π and π-π stacking interactions.

Electronic Transport Properties of a Naphthopyran-Based Optical Molecular Switch: an ab initio Study

The electronic transport properties of a naphthopyran-based molecular optical switch are investigated by using the nonequilibrium Green's function formalism combined with first-principles density functional theory.The molecule that comprises the switch can convert between its open and closed forms upon photoexcitation.Theoretical results show that the current through the open form is significantly larger than that through the closed form,which is different from other optical switches based on ring-opening reactions of the molecular bridge.The maximum on-off ratio(about 90)can be obtained at 1.4 V.The physical origin of the switching behavior is interpreted based on the spatial distributions of molecular orbitals and the HOMO-LUMO gap.Our result shows that the naphthopyran-based molecule is a good candidate for optical molecular switches and will be useful in the near future.

Michael Addition Reaction without Catalyst: The Synthesis of 2-Amino-5, 6, 7, 8-tetrahydro-5-oxo-4-aryl-7, 7-dimethyl- 4H-benzo-[b]-pyran Derivatives

A series of tetrahydrobenzo-[b]-pyran derivative was synthesized by the reaction of arylmethylene malononitrile or arylmethylene cyanoacetate with dimedone in ethylene glycol at 80C without catalyst. The structures of the two products were characterized by X-ray diffraction.

Preparation of 3,4-Dihydro-2H-pyran Catalyzed by Modified Gamma Alumina

A promising catalytic material, modified ga mma alumina with high surface area (300m2/g) and higher c ontents of strong acid sites was developed. It was prepared by a special precip itation method with aluminum nitrate solution containing a certain amounts of or thosilicic acid and ammonia aqueous solution. Compared with commercial gamma alu mina, the modified gamma alumina is an effective catalyst for dehydration of tet rahydrofurfuryl alcohol to 3,4-Dihydro-2H-pyran.Under the optimized reaction conditions, an improved yield of 3,4-Dihydro-2H-pyran of 93.4% was achieved. The profiles of pyridine TPD show that the modified gamma alumina exhibits more strong acid sites than that in the commercial gamma alumina, indicating the stro ng acid sites on the surface of the catalyst may play a crucial role in this rea ction.

Synthesis and Biological Evaluation of Pyranone Analogues of Territrem B

23 compounds containing pyranone pharmacophore of territrem B were designed and synthesized. Some of the analogues showed IC50 values of AChE inhibition at 10^-5 mol/L.

Synthesis and Structure of Ethyl 3-acetamido-4-aryl-6-methyl-2-oxo-3,4-dihydropyran-5-carboxylates

Two ethyl 3-acetamido-4-aryl-6-methyl-2-oxo-3,4-dihydropyran-5-carboxylates（3） were synthesized with high diastereoselectivities and characterized by IR,NMR and MS.The configuration of 3a was confirmed by single-crystal X-ray diffraction,ethyl 3-acetamido-4-（4-nitrophenyl）-6-methyl-2-oxo-3,4-dihydropyran-5-carboxylate（3a）,C17H18N2O7.The crystal is of orthorhombic,space group Pbca with a = 11.7781（16）,b = 9.5979（10）,c = 32.115（3）,V = 3630.4（7）3,Z = 8,Mr = 362.33,Dc = 1.326 Mg/m^3,λ = 0.71073,μ（MoKα） = 0.104 mm^-1,F（000） = 1520,the final R = 0.0646 and wR = 0.1464 for 1788 observed reflections with I 〉 2σ（I）.The N-H and oxygen atom are involved in intermolecular hydrogen bonds which link the molecules into a one-dimensional chain and stabilize the structure.

Synthesis and Antibacterial Activities of Pyran Annulated Heterocyclic Compounds

Two novel pyran annulated heterocyclic compounds （1 and 2） were synthesized and characterized via IR, lH NMR and H RMS. The structure of compound 1 was verified by single-crystal X-ray diffraction. The in vitro antibacterial activities of the two compounds against Staphylococcus aureus （S. aureus ATCC 29213）, methicillin-resistant S. aureus （MRSA XJ 75302）, vancomycin-intermediate S. aureus （Mu50 ATCC 700699）, and USA 300 （Los Angeles County clone, LAC） were evaluated by observing the minimum inhibitory concentration.

Synthesis,Crystal Structure and Anti-tumor Activity of Ethyl 3-(4-methoxyphenyl)-4-oxo-3,3a,4,6-tetrahydro-1H-furo[3,4-c]pyran-3a-carboxylate

The title compound（ethyl 3-（4-methoxyphenyl）-4-oxo-3,3a,4,6-tetrahydro-1H-furo[3,4-c]pyran-3a-carboxylate） has been synthesized,and its crystal structure was characterized by X-ray single-crystal diffraction.The crystal belongs to monoclinic,space group P21/n,with a = 10.124（4）,b = 11.754（4）,c = 13.792（5） ,β = 111.533（3）o,V = 1526.6（10） 3,Z = 4,C17H19O6,Mr = 319.32,Dc = 1.389 g/cm3,F（000） = 676,λ（MoKα） = 0.71073 ,μ = 0.105 mm-1,R = 0.0660 and wR = 0.2027 for 2993 observed reflections（I 2σ（I））.The compound shows potent anti-tumor activity in vitro.

KF-Al₂O₃as an Efficient and Recyclable Basic Catalyst for the Synthesis of 4<i>H</i>-Pyran-3-carboxylates and 5-Acetyl-4<i>H</i>-pyrans

KF-Al2O3 as a recyclable basic catalyst for the three-component synthesis of 4H-pyran derivatives by the reaction of aldehydes, malononitrile and active methylene dicarbonyl compounds in ethanol at room temperature is described. The protocol is environmentally benign and offers rapid access to a wide array of 4H-pyran heterocycles in good to excellent yields.

Synthesis and Evaluation of 2-Amino-4H-Pyran-3-Carbonitrile Derivatives as Antitubercular Agents

A series of 2-amino-4H-pyran-3-carbonitrile derivatives were designed and synthesized. Their antitubercular activities were evaluated against autoluminescent M. tuberculosis H37Ra and standard strain M. tuberculosis H37Rv. No obvious antitubercular activities could be observed (MIC > 10 ug/mL). The results are in sharp contrast with the previously reported data.

Synthesis and Molecular Structure of Acetic Acid-3,5-diacetoxy-2-acetoxymethyl-6-(4-quinoxalin-2-yl-phenoxy)-tetrahydro-pyran-4-yl-ester

The title compound, acetic acid-3,5-diacetoxy-2-acetoxymethyl-6-（4-quinoxalin- 2-yl-phenoxy）-tetrahydro-pyran-4-yl-ester 8 （C28H28N2O10, Mr = 552.54）, has been synthesized and its crystal structure was determined by X-ray diffraction analysis. It crystallizes in monoclinic, space group P21, a = 10.060（8）, b = 5.648（4）, c = 24.11（2）A, β = 91.078（10）°, Z = 2, V= 1369.9（19）A^3, Dc = 1.339 g/cm^3,μ（MoKa） = 1.03 cm^-1, F（000） = 580.00, T =. 193.1 Kx-9 θmax = 25.03, （△/σ）max = 0.0000, Flack = -0.0（24）, the final R = 0.0680 and wR = 0.140 （w = 1/[0.0016Fo^2 ＋ 1.00000（Fo^2）]/（4Fo^2）） for 3126 observed reflections （1 〉 20（/））. The pyranoid ring adopts chair conformation in the sugar moiety, and all of the acetyl groups are in the e bond of the pyranoid ring, so the sugar moiety is very stable.

Syntheses, Characterization and Biological Activity of Coordination Compounds of 3-Hydroxy-2-methyl-4<i>H</i>-pyran-4-one and Its Mixed Ligand Complexes with 1,2-Diaminocyclohexane

Coordination compounds of 3-hydroxy-2-methyl-4H-pyran-4-one with iron(III), cobat(III) and chromium(III) were synthesized with M:L (1:2). Mixed ligand coordination compounds of 3-hydroxy-2-methyl-4H-pyran-4-one and 1,2-diaminocyclohexane using the same metal ions were also synthesized M:L1:L2 (1:1:1) where L1 is 3-hydroxy-2-methyl-4H-pyran-4-one and L2 is 1,2-diaminocyclohexane. The coordination compounds obtained were characterized using electronic and infrared spectral analyses, magnetic susceptibility and percentage metal analysis. They were also evaluated for their cytotoxic and antioxidant activities. The result obtained suggested that octahedral geometry was obtained for all the compounds, as a result of additional two molecules of the solvent coordinated to the metal ions. Both the primary and secondary ligands coordinated in a bidentate fashion. The synthesized compounds exhibited moderate cytotoxicity, although none was as active as the standard. The cobalt(III) mixed ligand complex elicited the highest activity. The synthesized compounds all exhibited good to moderate antioxidant activity.

Synthesis and Crystal Structure of Methyl(7,7-Dimethyl-2-amino-4-(4-chlorophenyl)-5-oxo-5,6,7,8-tetrahydro-4H-benzo-[b]-pyran-3-yl)Carboxylate

The title compound methyl (7,7-dimethyl-2-amino-4-(4-chlorophenyl)-5-oxo- 5,6,7,8-tetrahydro-4H-benzo-[b]-pyran-3-yl) carboxylate (C19H20ClNO4, Mr = 361.81) was synthesized and crystallized. The crystal belongs to triclinic, space group P ī with a = 8.519(2), b = 10.346(2), c = 11.481(3) ?, ( = 108.16(1), ( = 107.78(2), ( = 91.83(2)(, Z = 2, V = 906.5(3) ?3, Dc = 1.326 g/cm3, ((MoK() = 0.234 mm-1, F(000) = 380, R = 0.0467 and wR = 0.1270 for 3142 observed reflections (I ( 2((I)). X-ray analysis reveals that the C(7), C(8), C(9), O(1), C(10) and C(11) atoms form a six-membered ring which adopts a boat conformation. In the ring, the distances of C(8)-C(9) and C(10)-C(11) are 1.332(3) and 1.357(3) (A), respectively, which indicates that they are C=C double bonds. Another six-membered ring (C(8)-C(9)-C(15)-C(14)-C(13)-C(12)) adopts the half-chair conformation. In addition, there are intermolecular hydrogen bonds in the crystal structure.