Palladium-Catalyzed C–H Arylation of Benzofurans with Triarylantimony Difluorides for the Synthesis of 2-Arylbenzofurans

Pd-catalyzed regioselective C–H arylation is a useful tool for the chemical modification of aromatic heterocycles and 2-arylbenzofuran derivatives are of interest as biologically active substances. Herein, the reaction of triarylantimony difluorides with benzofurans under aerobic conditions in 1,2-DCE, using 5 mol% Pd (OAc)₂ and 2 eq. of CuCl₂ at 80 °C, produced a variety of 2-arylbenzofurans in moderate-to-high yields. The reaction is sensitive to the electronic nature of the substituents on the benzene ring of the triarylantimony difluorides: an electron-donating group showed higher reactivity than an electron-withdrawing group. Single crystal X-ray analysis of tri(p-methylphenyl) antimony difluoride revealed that the central antimony atom exhibits trigonal bipyramidal geometry.     

2-(5-Hydrazinocarbonyl-2-thienyl) -5, 6-methylenedioxybenzofuran and 2-(5-hydrazinocarbonyl-2-furyl)-5, 6-methylenedioxybenzofuran as novel fluorescence derivatisation reagents for carboxylic acids in liquid chromatography

The new acid hydrazides, 2-(5-hydrazinocarbonyl-2-thienyl)-5,6-methylenedioxybenzofuran (TMBH) and 2-(5-hydrazin-ocarbonyl-2-furyl)-5, 6-methylenedioxybenzofuran (FMBH), were synthesized as precolumn fluorescence derivatisation reagents for carboxylic acids in liquid chromatography. These compounds readily react with carboxylic acids in the presence of a coupling reagent under mild conditions in aqueous solution to give fluorescent derivatives. The detection limits of lauric acid were both 0.1 pmol per 10 μl injection volume at a signal-to-noise ratio of 3. The methods in which these compounds are used were applied to the assay of a standard mixture of prostaglandins (25 μM) and prostaglandins in a human seminal fluid.     

Benzofuran trimers for organic electroluminescence

Four linear benzofuran trimers have been prepared by a two-stage synthetic procedure. They were tested as materials for organic electroluminescence (OEL). Precursor phenylene ethynylene oligomers were formed in the first stage, then after removal of the phenolic hydroxyl protecting groups, a base was used to promote the cyclization of ortho-hydroxy phenylene ethynylenes to benzofurans. Both acetate esters and tert-butyl carbonates were employed as protecting groups. tert-Butyl and n-hexyl substituents on the benzofurans were used to modulate solubility, aggregation, and film-forming properties; two tert-butyl groups prevented aggregation in the solid state, thus maintaining emission in the blue region of the visible spectrum. The OEL characteristics of the tert-butyl-substituted benzofuran trimer were explored, and blue emission was observed. The two-stage synthetic procedure employed for the preparation of these benzofuran trimers may be applied to a wide variety of benzofuran oligomer and polymer targets.     

Synthesis and Crystal Structure of （5-Hydroxy-6-methoxybenzofuran- 3-yl）-（4-methoxyphenyl）methanone

Compound 1 (5-hydroxy-6-methoxybenzofuran-3-yl)(4-methoxyphenyl)methanone, C17H14O5 , as a potential anti-breast cancer agent has been synthesized under microwave irradiation, which was further converted to (5,6-dihydroxybenzofuran-3-yl)(4-methoxyphenyl)methanone (2). The compounds were characterized by MS and NMR spectra. Meanwhile, the crystal of 1 was obtained and determined by X-ray single-crystal diffraction. Crystal data: monoclinic system, space group P21/n, a=8.908(6), b=10.505(7), c=15.452(11), β=105.043(9)°, V=1396.4(16)3 , Z=4, F(000)=624, Dc=1.419 g/cm3 , μ=0.105 mm1, R=0.0513 and wR=0.1246 for 14459 independent reflections (Rint=0.0647) and 2488 observed ones (I>2σ(I)). Intermolecular O-H···O and π-π stacking interactions contributed to the stability of the structure.     

A Novel and Facile Synthesis of 2‐(Benzofuran‐2‐yl)benzo[h]quinoline‐3‐carboxylic Acid Derivatives

A simple and concise approach for the synthesis of a series of new heterocyclic systems of 2‐(benzofuran‐2‐yl)benzo[h]quinoline‐3‐carboxylic acid derivatives ( 3a–3g ) is described. The synthetic strategy features the one‐pot reaction of ethyl 2‐(chloromethyl)benzo[h]quinoline‐3‐carboxylate ( 2 ) with various substituted salicylaldehydes as well as 2‐hydroxy‐1‐naphthaldehyde as a key step. The substrate 2 was prepared in good yield by a mild, efficient and direct reaction of 1‐naphthylamine ( 1 ) with Vilsmeier‐Haack reagent. The structures of all the new compounds were identified by spectral data and elemental analysis.     

Visible light‐induced diastereoselective E/Z‐photoisomerization equilibrium of the C=C benzofuran‐3‐one‐hydantoin dyad

The diastereoselective photodependent isomerization equilibrium of E/Z‐1,3‐ditolyl‐5‐[3‐oxobenzofuran‐2(3H)‐ylidene]imidazolidine‐2,4‐dione ( 5 ) is reported. Both diastereomers E-5 and Z-5 are stereochemically stable in solid state but show significant photosensibility in solutions of halogenated solvent. The photoisomerization equilibrium of E/Z‐ 5 is therefore deduced from the ¹H NMR profile after visible‐light irradiation of both E-5 and Z-5 samples. The results of the kinetic study, monitored by UV‐HPLC, reveal that the E/Z equilibrium is diastereoselective and photodependent, being the transformation E ? Z proceeding faster than that of Z ? E, and the E/Z ratio at the equilibrium depends on the used solvent, light source, and temperature. Both diastereomers are visible‐light photosensitive tending to coexist together in equilibrium solutions at a determined ratio, which is always in favor of the Z‐product assuming a minimum thermodynamic energy and an increased entropy of the system. Time‐dependent density functional theory calculations suggest that the photoisomerization mechanism proceeds via a conical intersection involving the first‐excited state: Upon irradiation, the E-5 isomer is excited to the S1 potential energy surface, where it relaxes through rotation of the C=C bond and reaches a conical intersection with the ground‐state potential energy surface, thus yielding the Z-5 isomer. Copyright © 2014 John Wiley & Sons, Ltd.     

Two New Benzofuran Derivatives from Ligularia stenocephala

Two new benzofuran derivatives were isolated from the roots ofLigularia stenocephala.Their structures were established by spectroscopic methods and 2D NMR experiments.     

2,3-Dihydrobenzofuran-3-one in the Synthesis of 3-Cyano-2-imino-1-p-nitrophenyl-1,2-dihydropyrido[3,2-b]benzofuran

3-p-Nitrophenylaminobenzofuran was obtained by the reaction of 2,3-dihydrobenzofuran-3-one with p-nitroaniline and was used in the Vilsmeier reaction for the synthesis of 2-formyl-3-p-nitrophenylaminobenzofuran. Treatment of the latter with malononitrile led to 1-p-nitrophenyl-2-imino-3-cyano-1,2-dihydropyrido[3,2-b]benzofuran.     

ORGANISCHE PHOSPHORVERBINDUNGEN 85.1 HERSTELLUNG,EIGENSCHAFTEN UND BIOLOGISCHE WIRKUNG VON N-AMINOGLYPHOSATE UND AZAGLYPHOSATE

Abstract

The synthesis and the chemical, physical and spectral properties of N-aminoglyphosate ethylester (hydrazino-N′-carbethoxymethyl-N′-methylphosphonic acid) 4a, H₂OPCH₂N(NH₂)CH₂CO₂C₂H₅, of hydrazino-N′-carbethoxymethyl-N′-methyl-P-methylphosphinic acid 4b, CH₃(HO₂)PCH₂N(NH₂)-CH₂CO₂C₂H₅, and of azaglyphosate ethylester (hydrazino-N-carbethoxymethyl-N-methyl-phosphonic acid 9, H₂O₃PCH₂NHNHCH₂CO₂C₂H₅, are described. 4a, 9 and 10 exhibit plant growth regulating properties.     

Synthesis of [b]-Fused Benzo[d]furano Heterocycles

In the reactions of 3,4,6,7-tetrachloro-2,5-dihydroxy-2,3-dihydrobenzo[b]furan with 4-methyl and 4-phenyl thiosemicarbazides, dithizone and sodium N,N-diethyldithiocarbamate the [b]fused benzo[d]furano heterocycles have been synthesized.