Se-mediated one-pot synthesis of 2-substituted benzoselenazole derivatives from 2 to iodoanilines and arylacetic acids/arylmethyl chlorides

A general approach to the formation of 2-substituted benzoselenazoles from the three-component reactions of 2-iodoanilines, selenium powder, arylacetic acids or benzyl chlorides is described. The use of copper salt as catalyst and dimethyl sulfoxide (DMSO) as solvent are crucial to afford the title compounds in moderate to good yields (45–88%) with good functional group tolerance on the aromatic and heteroaromatic substrates.     

Facile one-pot preparation of 5-aryltetrazoles and 3-arylisoxazoles from aryl bromides

The successive treatment of aryl bromides with n-BuLi, DMF, hydroxylamine hydrochloride, and finally diphenylphosphoryl azide provided efficiently the corresponding 5-aryltetrazoles in good to moderate yields. Similarly, the successive treatment of aryl bromides with n-BuLi, DMF, hydroxylamine hydrochloride, and finally diethyl acetylenedicarboxylate and Oxone^® provided efficiently the corresponding diethyl 3-arylisoxazole-4,5-dicarboxylates in good to moderate yields. Aromatic aldoximes are the key intermediates in both reactions, and 5-aryltetrazoles and 3-arylisoxazoles could be obtained from aryl bromides in one pot under transition-metal-free conditions.     

Facile one-pot synthesis of 2,3,5-substituted 1,2,4-oxadiazolines from nitriles in aqueous solution

[reaction: see text] Alkyl/aryl amidoximes, prepared from the corresponding nitriles and N-alkylhydroxylamines, have readily undergone consecutive Michael additions to electron-deficient alkynes and provided highly substituted 1,2,4-oxadiazolines in good yields in homogeneous aqueous solution.     

Facile one-pot synthesis of tetrahydroisoquinolines from amino acids via hypochlorite-mediated decarboxylation and Pictet–Spengler condensation

A convenient method for oxidative decarboxylation of α-amino acids is presented. The aldehyde products may be isolated or converted to tetrahydroisoquinolines by addition of dopamine via Pictet–Spengler reaction. Racemic products are generated by phosphate buffer >300 mM to maximize regioselectivity. (S)-Enantiomer products are generated by norcoclaurine synthase reaction in maleic acid buffer to minimize chemical background reaction.     

Oxidative decarboxylation of arylacetic acids by means of tetrabutylammonium periodate

Tetrabutylammonium periodate (TBAPI) in refluxing dioxane is able to convert arylacetic acids into the corresponding nor-aldehydes in good yields.     

Effects of non-ionic surfactants on isotachophoretic separations of 2-arylpropionic acids

Non-ionic surfactant (Brij 35, Tween 20, Tween 80 and Tergitol NPX) modified capillary isotachophoresis was investigated for the separation of 2-arylpropionic acids (fenoprofen, flurbiprofen, ibuprofen, ketoprofen and naproxen) and benzoic acid and its derivatives (salicylic, acetylsalicylic and gallic acids). The relative step height (RSH) values of analytes were found to be dependent on the type and concentration of the surfactant. The strength of the affinity of the 2-arylpropionic acids to the non-ionic micelles was found to be as follows: flurbiprofen > fenoprofen > ibuprofen > naproxen > ketoprofen. In general, the RSH values of 2-arylpropionic acids increase with an increase in the concentration of surfactants. However, the RSHs of benzoic, salicylic and gallic acids are not considerably affected. Separation of all acids was obtained with the Tween 20 (1.5%, w/v) in the leading electrolyte 10 mmol L(-1) hydrochloric acid/L-histidine (pH 6.0). Changes in the fluorescence intensity of fenoprofen, flurbiprofen and naproxen were also investigated in micellar media (Tween 20, Tween 80 and Brij 35). The strength of the affinity of the 2-arylpropionic acids to the Tweens micelles was found to be as follows: flurbiprofen > fenoprofen > naproxen, which is consistent with the isotachophoretic results. On the contrary, the strength of the affinity to the Brij micelles was found to be as follows: fenoprofen > naproxen > flurbiprofen.     

Facile one-pot synthesis of N-difluoromethyl-2-pyridone derivatives

[reaction: see text] A novel one-pot synthesis of N-difluoromethyl-2-pyridones is described. N-(Pyridin-2-yl)acetamide derivatives were excellent precursors for the preparation of N-difluoromethyl-2-pyridone derivatives. Difluoromethylation of 2-acetaminopyridine derivatives was achieved with sodium chlorodifluoroacetate as a difluorocarbene source in the presence of a catalytic amount of 18-crown-6. Subsequent in situ hydrolysis of resultant 1,2-dihydro-2-acetimino-1-difluoromethylpyridines proceeded under mild acidic conditions to afford the corresponding N-difluoromethyl-2-pyridones in moderate to good yields.     

Photoreactivity of the nonsteroidal anti-inflammatory 2-arylpropionic acids with photosensitizing side effects.

The photoreactivity of the nonsteroidal anti-inflammatory 2-arylpropionic acids benoxaprofen, carprofen, naproxen, ketoprofen, tiaprofenic acid, and suprofen is reviewed with special emphasis on fundamental photophysical and photochemical properties. The absorption and emission properties of the excited states of these drugs as well as their main photodegradation routes are summarized. The photochemical mechanisms are discussed on the basis of product studies and detection of short-lived intermediates by means of laser flash photolysis. After dealing with the unimolecular processes, attention is focused on the photosensitized reactions of key biomolecules, such as lipids, proteins or nucleic acids. Finally, a short section on the photobiological effects on simple biological models is also included. Although some earlier citations are included, the literature coverage is in general limited to the last decade.     

Cobalt-catalyzed synthesis of α-arylpropionic and diarylacetic acids

The cobalt-catalyzed carbonylation of ArCH(R)X (R = CH₃, C₆H₅; X = Cl, Br) in alcoholic solvents under atmospheric pressure of CO is reported. Selective, high yield syntheses of the corresponding acids ArCH(R)COOH can be achieved within a very narrow range of experimental conditions by controlling kinetically the reversible interconversion of intermediate aryl and alkylcobalt complexes. The important roles of the base and of the alcoholic medium are briefly discussed.     

Iron(III) triflate-catalyzed one-pot synthesis of acetal-type protected cyanohydrins from carbonyl compounds

A variety of cyanohydrin THP ethers were readily prepared from carbonyl compounds with trimethylsilyl cyanide and tetrahydropyran-2-yl acetate under the influence of a catalytic amount of iron(III) triflate in a convenient one-pot procedure. This method was also effective to prepare O-protected cyanohydrins by various acetal-type protective groups.     

Enantiomeric separation and detection by high-performance liquid chromatography-mass spectrometry of 2-arylpropionic acids derivatized with benzofurazan fluorescent reagents

The enantiomneric separation and the detection of 2-arylpropionic acids after derivatization with the fluorescent reagents with a benzofurazan structure, ( S )-(+)-4-( N,N -dimethylaminosulphonyl)-7-(3-aminopyrrolidin-1-yl)-2,1,3-benzoxadiazole (( S )-DBD-Apy), (R)-(-)-4-nitro-7-(3-aminopyrrolidin-1-yl)-2,1,3-benzoxadiazole (( R )-NBD-Apy), 4- N,N -dimethylaminosulphonyl-7-piperazino-2,1,3-benzoxadiazole (DBD-PZ) and N -hydrazinoformylmethyl- N -methylamino-4,4- N,N -dimethylaminosulphonyl-2,1,3-benzoxadiazole (DBD-CO-Hz) by high-performance liquid chromatography (HPLC) and electrospray ionization mass spectrometry (ESI-MS) were examined. The diastereomeric derivatization with ( S )-DBD-Apy or ( R )-NBD-Apy and the separation on the reversed phase column afforded the high sensitivity. The separation on chiral stationary phase after non-chiral derivatization with DBD-PZ or DBD-CO-Hz provided less sensitivity. The signal-to-noise ratio of ( S )-DBD-Apy-( S )-ketoprofen of 200:1 was observed for 12.5 picomole (pmol) injection and selected ion monitoring (SIM) of the quasi-molecular ion after splitting 1:7 before entering into the electrospray ion sources. As a result, the usefulness of these reagents for MS detection has been demonstrated. © 1998 John Wiley & Sons, Ltd.     

Facile,eco-friendly,one-pot protocol for the synthesis of indole-imidazole derivatives catalyzed by amino acids

An efficient, convenient green approach for the synthesis of indole-based 2,4,5-trisubstituted and 1,2,4,5-tetrasubstituted imidazoles by multicomponent reaction of substituted 2-arylindole-3-carbaldehydes, benzil, substituted anilines, and ammonium acetate using catalytic amino acid (glycine) in ethanol is described. Several amino acids have also been evaluated as organic catalysts for these reactions. The structures of the compounds have been established on the basis of infrared, mass, and ¹H NMR spectral data. The mild reaction conditions, inexpensive/economical reagents, and good yield show the usefulness of this approach.     

Facile one-pot preparation of thermally and photochemically convertible soluble precursors of copper phthalocyanine and naphthalocyanine

Soluble copper phthalocyanine (CuPc) and naphthalocyanine (CuNc) precursors which can be converted thermally and photochemically into insoluble CuPc and CuNc, respectively, have been synthesized by a one-step reaction using commercially available chemicals.     

Facile preparation of recyclable biocatalyst-decorated magnetic nanobeads in aqueous media

A facile process was developed to manufacture biocatalyst-conjugated magnetic nanobeads, which afford no loss of the intrinsic activity and enantioselectivity of biocatalysts. Up to 90% of their activities remained after six-time recycling in aqueous media.     

Facile one-pot syntheses of bromoacetylenes from bulky trialkylsilyl acetylenes

Because haloalkynes are versatile intermediates in synthetic chemistry, the development of new efficient methods for the conversion of 1-trialkylsilylacetylenes to haloacetylenes in situ remains desirable, especially when the corresponding terminal acetylenes are unstable. Using AgF and NBS, we have successfully transformed various 1-(trialkylsilyl)acetylenes, including bulky trialkylsilyl acetylenes, into bromoacetylenes in high yield. The reactions are chemoselective: triisopropylsilyl ethers were not deprotected under these conditions.     

Facile preparation of cyclopropanes from 2-iodoethyl-substituted olefins and 1,3-dihalopropanes with zinc powder

Two efficient, simple, cheap, and environmentally benign preparations of cyclopropanes were achieved. One is the formation via 3-exo-trig manner from various electron-deficient 2-iodoethyl-substituted olefins with zinc powder in a mixture of t-butyl alcohol and water, and the other is the formation via 3-exo-tet manner from various 1,3-dihalopropanes with zinc powder in ethanol.     

"一锅法"简便合成一芳基硼酸和二芳基硼酸

本文改进了一芳基硼酸和二芳基硼酸的制备方法. 利用芳卤, 镁屑, 硼酸三正丁酯或三氟化硼乙醚溶液在室温下"一锅"反应简便合成一芳基硼酸和二芳基硼酸, 分离产率为48～80% .     

Mild,one-pot preparation of 2-substituted benzimidazoles from organic halides

Alkyl halides are feasibly transformed into benzimidazoles by a domino reaction under solvent-free conditions. The organic halides react with o-phenylenediamines in stoichiometric amounts in the presence of pyridine-N-oxide to produce the desired substituted benzimidazoles. This domino synthesis does not require catalysts. The synthesis occurs in dry medium and the environmental impact is minimal. The method provides products without intermediate separation. A mechanism of benzimidazole synthesis is also proposed.     

Facile one-pot green synthesis of tetrahydrobiphenylene-1,3-dicarbonitriles in aqueous media under ultrasound irradiation

Research on Chemical Intermediates - An efficient and rapid procedure for the synthesis of 16 novel tetrahydrobiphenylene-1,3-dicarbonitrile derivatives (4a–p) is described, employing the...     

Rapid one-pot preparation of 2-substituted benzimidazoles from 2-nitroanilines using microwave conditions

A high yielding one-pot procedure for the generation of 2-substituted benzimidazoles directly from 2-nitroanilines by in situ reduction and cyclization using a microwave procedure is described.