Synthesis of Bioactive Side‐Chain Analogues of TAN‐2483B

The fungal metabolite TAN‐2483B has a 2,6‐trans‐relationship across the pyran ring of its furo[3,4‐b]pyran‐5‐one core, which has thwarted previous attempts at its synthesis. We have now developed a chiral pool approach to this core and prepared side‐chain analogues of TAN‐2483B. The synthesis relies on ring expansion of a reactive furan ring‐fused dibromocyclopropane and alkynylation of the resulting pyran. The furan ring is constructed by palladium‐catalysed carbonylative lactonisation. Various side‐chains are appended through Wittig‐type chemistry. The prepared analogues showed micromolar activity towards cancer cell lines HL‐60, 1A9 and MCF‐7 and certain human disease‐relevant kinases, including Bruton's tyrosine kinase (Btk).     

POLYMERIZATION OF A NEW SUBSTITUTED ACETYLENE BEARING A FURAN RING WITH PALLADIUM ACETYLIDE CATALYSTS

A substituted polyacetylene bearing a furan ring, poly(2-propynyl 2-furoate) (PPF), was synthesized for the first time with palladium acetylide complex catalysts in CHCl3 at 60℃ to give a soluble and stable polymer with a yield of ca.75%. Some features for polymerization of 2-propynyl 2-furoate are described and discussed. The resulting polymer was characterized by IR, GPC and ^1H-NMR analysis.     

Enantioselective Synthesis of (−)‐Halenaquinone

The efficient, 12–14 step (LLS) total synthesis of (?)‐halenaquinone has been achieved. Key steps in the synthetic sequence include: (a) proline sulfonamide‐catalyzed, Yamada–Otani reaction to establish the C6 all‐carbon quaternary stereocenter, (b) multiple, novel palladium‐mediated oxidative cyclizations to introduce the furan moiety, and (c) oxidative Bergman cyclization to form the final quinone ring.     

Synthesis and characterization of square-planar palladium(II) complexes containing anti- and syn-furan-2-aldoxime

Summary Fifteen palladium(II) square-planar complexes containing monodentate and/or bidentate anti- and syn-furan-2-aldoxime (FDH) have been isolated and characterized by elemental analysis, molecular weight determination, conductance studies, magnetic moments and i.r. spectral studies. The monodentate ligand coordinates through the nitrogen atom while the bidentate ligand coordinates through the furan oxygen atom and the nitrogen atom. The C-O-C stretching frequency of the furan ring may be taken as the criterion for the denticity of this ligand and is observed at 1240 and 1270 cm^– in anti- and syn-furan-2-aldoxime respectively. A shift to lower frequency occurs (in the complex) if the ligand is bidentate, however this frequency is unaffected if the ligand is monodentate.     

Synthesis of conformationally restricted 2,3-diarylbenzo[b]furan by the Pd-catalyzed annulation of o-alkynylphenols: exploring a combinatorial approach

The palladium/bpy-catalyzed annulation of o-alkynylphenol with various aryl halides to generate diversified 2,3-diarylbenzo[b]furan is herein described. This method provides an efficient synthetic pathway for the combinatorial synthesis of conformationally restricted 2,3-diarylbenzo[b]furan for drug discovery.     

Furoyl phosphonates

A series of furoyl phosphonates bearing methyl, methoxymethyl, and diethoxyphosphorylmethyl groups in the furan ring have been synthesized via the Arbuzov reaction from the corresponding acid chlorides. NMR spectral parameters of the prepared compounds were studied. The values of coupling constants between the phosphorus nuclei and the carbon nuclei of the furan ring have been examined with relation to the location of the acylphosphoryl group in the furan ring, the nature of second substituent, and location of the latter with respect to the phosphorus-containing substituent in the furan ring. The substitution in position 4 of the furan ring of 3-furoyl phosphonates has been shown to strongly decrease the value of the coupling constant between the phosphorus nucleus and the C² atom of the heterocycle. The interaction between the phosphorus nuclei has not been detected in the spectra of the compounds containing both diethoxyphosphorylmethyl and acylphosphonate fragments.     

Efficient Heterogeneous Palladium‐Catalyzed Oxidative Cascade Reactions of Enallenols to Furan and Oxaborole Derivatives

A heterogeneous palladium‐catalyzed oxidative cyclization of enallenols has been developed for the construction of highly substituted furan and oxaborole derivatives. The heterogeneous catalyst (Pd‐AmP‐MCF) exhibits high activity, high site‐ and stereoselectivity, and efficient palladium recyclability in the transformations.     

Strain-Induced Ring Expansion Reactions of Calix[3]pyrrole-Related Macrocycles

The recent discovery of calix[3]pyrrole, a porphyrinogen-like tripyrrolic macrocycle, has provided an unprecedented strain-induced ring expansion reaction into calix[6]pyrrole. Here, we synthesized calix[n]furan[3-n]pyrrole (n=1∼3) macrocycles to investigate the reaction scope and mechanism of the ring expansion. Single crystal X-ray analysis and theoretical calculations revealed that macrocyclic ring strain increases as the number of inner NH sites increases. While calix[1]furan[2]pyrrole exhibited almost quantitative conversion into calix[2]furan[4]pyrrole within 5 minutes, less-strained calix[2]furan[1]pyrrole and calix[3]furan were inert. However, N-methylation of calix[2]furan[1]pyrrole induced a ring-expansion reaction that enabled the isolation of a linear reaction intermediate. The mechanism analysis revealed that the ring expansion consists of regioselective ring cleavage and subsequent cyclodimerization. This reaction was further utilized for synthesis of calix[6]-type macrocycles.     

Infrared absorption spectra of functional derivatives of 5-nitrofurfuryl-2-polyalkenes and intramolecular interaction

The frequency characteristics of the vibration spectra of a number of polyalkene derivatives of 5-nitrofuran are examined. In particular, the IR spectra vibrations frequencies of the furan ring, nitro group, double bonds, and carbonyl group are examined with respect to the near and more remote intramolecular environment. The effects of intramolecular interaction, transmitted both through a chain of a 2-substituted system of the polyene type, and through a system of furan ring double bonds, are determined. The problem of the aromaticity of the furan ring is considered.     

呋喃环参与的Diels-Alder反应及其应用

呋喃环在作为Diels-Alder反应的二烯组份中得到了广泛的研究.本文就呋喃环参与的分子间和分子内D-A反应及其应用作一综述.     

Complexation properties of macrocyclic polyether-diester compounds containing furan and benzene subcyclic units

A new series of macrocyclic polyether-diester ligands containing a furan subcyclic unit is reported. In contrast to other macrocyclic ligands, the twenty-four membered ring diester compounds containing either a furan or benzene subcyclic unit complex more strongly with benzylammonium perchlorate than do the eighteen membered ring compounds.     

Oxybenziporphyrins, oxypyriporphyrins, benzocarbaporphyrins, and their 23-oxa and 23-thia analogues: synthesis, spectroscopic characterization, metalation, and structural characterization of a palladium(II) organometallic derivative

A series of nine porphyrin analogues have been synthesized using the "3 + 1" variant on the MacDonald condensation. Tripyrrane-type systems with a centrally unsubstituted pyrrole, furan, or thiophene ring were prepared using conventional methods, and these were condensed with indene-1,3-dicarbaldehyde, 5-formylsalicylaldehyde, or 3-hydroxy-2,6-pyridinedicarbaldehyde in the presence of TFA to generate benzocarba-, oxybenzi-, and oxypyriporphyrins, respectively. The furan-containing analogues proved to be highly basic and could only be isolated as the corresponding hydrochloride salts. All nine analogue systems showed porphyrin-like UV-vis spectra with one or two Soret absorptions near 400 nm and a series of weaker bands at longer wavelengths. These systems also showed large diatropic ring currents by proton NMR spectroscopy that were comparable to true porphyrins. In the presence of trace amounts of TFA, benzocarbaporphyrin 12 formed a monocation, and in 50% TFA a C-protonated dication was generated. The 23-oxacarbaporphyrin 14 gave a monocation in chloroform, although the free base was generated in 5% Et(3)N-chloroform. In 50% TFA-CHCl(3), 14 afforded a mixture of mono- and diprotonated species. Thiacarbaporphyrin 15 also formed a monocation in the presence of TFA, but C-protonation was relatively disfavored for this system. Nonetheless, in the presence of TFA-d, 12, 14, and 15 all showed rapid exchange of the internal NH and CH protons. Carbaporphyrin 12 also showed slow exchange at the meso-positions, but this process was not observed for its heteroanalogues 14 and 15. Protonation studies were also conducted for oxybenziporphyrins and oxypyriporphyrins 16-21. Oxacarbaporphyrin 14 was shown to be a superior organometallic ligand and afforded good yields of the related nickel(II) and palladium(II) derivatives under mild conditions. A low yield of the platinum(II) complex could also be isolated. All three complexes retained their aromatic character, although the Pd(II) derivative appeared to possess a slightly larger diatropic ring current. The palladium(II) complex 27 was further characterized by X-ray crystallography. The macrocyclic core was shown to be highly planar where the dihedral angles of the component pyrrole, furan and indene rings relative to the mean [18]annulene plane were all 相似文献   

Palladium(II)-mediated cascade carbonylative annulation of o-alkynyl-phenols on silyl linker-based macrobeads: a combinatorial synthesis of a 2,3-disubstituted benzo[b]furan library

[reaction: see text] A palladium(II)-mediated cascade carbonylative annulation of o-alkynylphenols was achieved successfully on silyl linker-based macrobeads, which led to an efficient combinatorial synthesis of a 2,3-disubstituted benzo[b]furan library.     

Furopyridines. XXXI. Birch reduction of furopyridines

Birch reduction of four furopyridines 1a‐d effected the characteristic cleavage of the furan ring, giving ethnylpyridinols 2a‐d , vinylpyridinols 3b,d , and ethylpyridinols 4a‐d , and the reduction of the furan ring, giving dihydrofuropyridine 5c,d.     

Synthesis,spectroscopy and metallation of mixed carbaporphyrinoid systems

Modified tripyrranes incorporating furan and thiophene rings were found to condense with benzene, pyridine and indene dialdehydes to give a series of novel porphyrin analogues, including thia- and oxa-carbaporphyrins; the latter readily forms nickel(II) and palladium(II) organometallic complexes.     

Catalytic ring opening of acetylcyclopropane by water and alcohols under the action of copper or palladium salts

The possibility of the cleavage of the C—C bond in acetylcyclopropane (ACP) under the action of water or alcohols in the presence of copper or palladium salts was demonstrated for the first time. At 175—180 °C, the reactions proceeded regioselectively with the cleavage of the C(1)—C(2) bond in the cyclopropane ring. The reaction of ACP with water afforded 5-hydroxypentan-2-one, bis(3-acetylpropyl) ether, and furan compounds, whereas the reactions with alcohols proceeded selectively to form 5-alkoxypentan-2-ones. The yields of the latter depend on the nature and structure of the alcohol, the maximum values (98%) being achieved in the case of primary alcohols.     

Fe<Subscript><Emphasis Type="Italic">n</Emphasis></Subscript> Clusters (<Emphasis Type="Italic">n</Emphasis> = 2–7) Interaction with Furan Ring: DFT Studies over Iron Surface Suitability for Furan Adsorption

The interaction of different iron clusters (Fe₂, Fe₃, Fe₄, Fe₅, Fe₆ and Fe₇) with furan compound was studied by density functional theory (DFT) and the results show that the compound possess suitable structural and electronic parameters for the metal adhesion. After analyzing the binding energy and molecular orbital studies, it is found that there is a bond between furan ring and metal. In the molecular orbital, since the HOMO localizes over furan ring, especially over C2=C3–C4=C5, the furan acts as donator (HOMO) and metal performs as acceptor (LUMO) in the interaction of furan with iron surface, transferring the high charge density mainly from the delocalization region of furan ring to the metal (L(σ) → Fe).     

An Approach toward 17-Arylsubstituted Marginatafuran-Type Isospongian Diterpenoids via a Palladium-Catalyzed Heck–Suzuki Cascade Reaction of 16-Bromolambertianic Acid

Isospongian diterpenes are a small but growing family of natural tetracyclic secondary metabolites isolated from marine organisms, primarily sponges and nudibranchs. A palladium-catalyzed domino Heck–Suzuki reaction sequence for the synthesis of the tetracyclic skeleton of marginatafuran-type isospongian diterpenoids with a wide variety of substituents in the C-17 position is reported. The proposed approach was based on selective transformations of the accessible plant diterpenoid lambertianic acid and includes an intramolecular Heck reaction of 16-bromolambertianic and arylation of the palladium intermediate with arylboronic acid. The influence of the nature of the substituent both in arylboronic acids and in the furan ring of 16-bromolambertianic acid on the direction and chemoselectivity of the reaction has been studied. The described derivatization of natural furanolabdanoid lambertianic acid produced new functionalized molecules for biological study and gave novel insights into the reactivity of complex molecular structures.     

碳核苷类似物的合成与生物活性

利用杂环金属盐法,通过呋喃碳核苷中间体,合成了哒嗪、哒嗪酮等碳核苷,讨论了反应机理;提高了呋喃汞盐法合成碳核苷的收率及立体选择性.     

Efficient Heterogeneous Palladium-Catalyzed Oxidative Cascade Reactions of Enallenols to Furan and Oxaborole Derivatives

A heterogeneous palladium-catalyzed oxidative cyclization of enallenols has been developed for the construction of highly substituted furan and oxaborole derivatives. The heterogeneous catalyst (Pd-AmP-MCF) exhibits high activity, high site- and stereoselectivity, and efficient palladium recyclability in the transformations.