Pechmann反应法制备香豆素的研究进展

综述了Pechmann反应法制备香豆素的研究进展。新型路易斯酸催化剂和微波技术的应用,可以高收率、高效率的合成广泛的香豆素衍生物。参考文献23篇。     

An Easy One-Pot Procedure for the Synthesis of <Emphasis Type="Italic">N</Emphasis>-Sulfonyl Phosphorous Ylides and Sulfonyl Iminophosphoranes

Summary. Reaction of triphenylphosphine and an electron deficient acetylenic ester in the presence of strong N–H acid such as alkyl and aryl sulfamides or acetamide produces phosphorous ylides at room temperature in CH₂Cl₂. The aryl sulfamide phosphoranes undergo a smooth transformation reaction in boiling toluene and produce iminophosphoranes.     

Investigation of the Structures of the Product Ions Produced via self-CI of Acetone

TheacetoneselfCImassspectrumAcetoneselfCImassspectrumisgiveninTable1.Table1.MajorproductionsandtheirrelativeabundanceofacetoneselfCIMSTheformationofionatmlZ73AnotherproductionintheselfCIMSofacetoneistheionatm/z73.InselfCIMSofacetone-d6,thecounterpartistheionatInjz82.InselfCIMSofthemixtureofacetoneandacetone-d6inaratioofl:l,thecorrespondingionsaretheionsatInlz73,76,79and82.TheirCIDreactionresultsarelistedinTable2.Table2.TheCIDMSoftheionatIn/z73andanalogsOnthebasisofthedatainTab…     

An iminophosphine dendrimeric ligand and its evaluation in the Heck reaction

DAB-dendr-(NH₂)₃₂ has been modified to produce two novel dendrimeric P,N-ligands, DAB-dendr-[1,2-(NCHC₆H₄PPh₂)]₃₂ and DAB-dendr-[1,2-(NHCH₂C₆H₄PPh₂)]₃₂. These were both found to activate electron rich aryl bromides in the Heck reaction. The reactions seem to proceed better in a novel solvent system consisting of an equimolar mixture of a tertiary amine with acetic acid. A marked dependence of the conversion on the [equivalents of dendrimeric ligand]/[Pd] ratio has been observed with conversion decreasing as the ratio of dendrimer equivalents to Pd increases. This phenomenon is attributed to interactions of the arms bearing the metal with neighboring ones within the dendrimer.     

New Facile Synthesis of 2-Aryloxy-5-(2-furfurylidene)- 4H-imidazolin-4-ones

Many N-heterocycles including 4H-imidazolin-4-ones exhibit biological activities1-3. Some derivatives of 5-(2-furfurylidene)-4H-imidazolin-4-one were found to show good antiinflammatory activity4. They can be synthesized by condensation of furfural with 5- unsubsituted 4H-imidazolin-4-ones or from corresponding oxazolones5,6. However, no synthesis of 2-aryloxy substituted 5-(2-furfurylidene)-4H-imidazolin-4-one was reported. Recently, aza-Wittig reaction has received increased attention …     

Investigation on property and mechanism of redox wave of methylhesperidine at Hg electrode

The voltammetric behaviors of methylhesperidine (MH) were studied by means of linear sweep voltammetry, cyclic voltammetry and normal pulse voltammetry. In the Brit-ton-Robinson buffer solutions with pH values from 2.05 to 6.37, MH could yield three reduction waves PC1,PC2 and PC3. PC1 wave is an adsorptive pre-wave. PC2 wave is an irreversible reduction of pre-protonated MH involving one electron and one proton. PC3 wave is an irreversible wave of reduction species radical of MH involving one electron.     

First synthesis of α-aminophosphonates from natural porphyrin derivatives by the Kabachnik—Fields reaction

A preparative procedure is proposed for the synthesis of α-aminophosphonates of natural porphyrins by the microwave-assisted Kabachnik—Fields reaction.__________Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 256–259, January, 2005.     

Synthesis of hydrophenanthrenes through a ‘green’ Fischer carbene-alkyne coupling process

Coupling of alkynylbenzoyl systems with γ,δ-unsaturated Fischer carbene complexes leads to the formation of hydrophenanthrene derivatives. This reaction is not affected by aqueous systems, which offer a further advantage such that chromium hexacarbonyl sublimes during the reaction process. Chromium carbene-alkyne coupling processes can thus be performed in environmentally friendly solvents with substoichiometric net consumption of chromium hexacarbonyl.     

Triplet states of humic acids studied by laser flash photolysis using different excitation wavelengths

The spectra and kinetics of short-lived intermediates formed from aqueous (0.1 N NaOH) solutions of the natural mixture of humic and fulvic acids (HFA) were studied by laser flash photolysis using excitation wavelengths of 337, 390, 470, and 520 nm. Laser photolysis of HFA with light of 520 and 470 nm results in the formation of triplet excited states (T_HFA) characterized by the broad absorption spectrum with a maximum near 630 nm and lifetimes of 0.15 ms in deoxygenated solutions. The formation of two types of T_HFA with lifetimes of 0.1 and 2 ms and absorption spectra with maxima at 570 nm is observed under photolysis with light of 337 and 390 nm. The estimation of quantum yields of T_HFA gives 1 and 0.3% under photolysis with excitation wavelengths of 337 and 520 nm, respectively. The rate constants of T_HFA quenching by molecular oxygen are equal to (7—8)·10⁸ L mol^–1 s^–1.