An improved Pfitzinger reaction for the direct synthesis of quinoline-4-carboxylic esters/acids mediated by TMSCl

An efficient and facile synthesis of quinoline-4-carboxylic esters/acids by TMSCl-promoted reaction of easily available N,N-dimethylenaminones and isatins in alcohols/water has been developed. The improved Pfitzinger reaction involves esterification and cyclization in one-step process, and in situ formed a carboxylic ester/acid group (CO₂R or COOH) at the 4-position of quinoline ring. Moreover, the key features of this protocol are readily available starting materials, good functional group tolerance, mild reaction conditions, operational simplicity, and feasibility of scale up.     

A new insight into the Pfitzinger reaction. A facile synthesis of 6-sulfamoylquinoline-4-carboxylic acids

The unusual formation of 6-sulfamoylquinoline-4-carboxylic acids from 5-sulfamoylisatins under the conditions of Pfitzinger reaction is described. Key step in the suggested mechanism is the reaction of in situ generated acetaldehyde with the hydrolytically cleaved isatin ring. The suggested mechanism has been confirmed by dynamic LCMS measurements and by reactions with isotopically labeled reactants.     

Metal-free one-pot synthesis of quinoline-2,4-carboxylates via a molecular iodine-catalyzed three-component reaction of arylamines,ethyl glyoxylate,and α-ketoesters

A simple and metal-free method has been developed for the construction of quinoline-2, 4-carboxylates under mild conditions via a molecular iodine-catalyzed three-component tandem reaction of arylamines, ethyl glyoxylate, and α-ketoesters. The present protocol provides a convenient and attractive approach to various quinoline-2, 4-carboxylates in moderate to good yields with excellent functional group tolerance.     

Efficient one-pot synthesis of ethyl 2-substitued-4-methylthiazole-5-carboxylates

A new and practical one-pot procedure for the synthesis of several 2-sustituted-4-methylthiazole-5-carboxylates from commercially available starting materials is described. Under mild reaction conditions, some of the products with alkyl group on the 2-amino group or with various groups on 2-substituted phenyl ring were obtained in good yields from ethyl acetoacetate, N-bromosuccinimide, thiourea, or its N-substituted derivatives in an efficient way instead of the traditional two-step reaction.     

Derivatives of benzothiadiazole-7-carboxylates: synthesis and biological activity

Salicylic acid (SA) and methyl jasmonate (MJ) are important plant signal molecules to cause systemic acquired resistance (SAR), while it’s reported that they also have wide spectrum antitumor activities. Benzothiadiazole-7-carboxylates are plant activators which can cause SAR just like SA and MJ. To investigate whether the benzothiadiazole-7-carboxylate family is endowed with anticancer activities, several benzothiadiazole-7-carboxylate derivatives are synthesized and their inhibition to P388 murine leukemia cell and A549 human lung cancer cell compared with MJ are evaluated. The data indicated that benzo-1,2,3-thiadiazole-7-carboxylic acid 2-benzoyloxyethyl ester has a higher inhibition ability to the cancer cell P388 and A549, compared with MJ. Correspondence: Yufang Xu, School of Pharmacy, East China University of Science and Technology, Shanghai 200237, China.     

An efficient one-step synthesis of 1,4-dihydropyridines via a triphenylphosphine-catalyzed three-component Hantzsch reaction under mild conditions

An efficient one-step synthesis of 1,4-dihydropyridines in good to excellent yields via the triphenylphosphine-catalyzed Hantzsch three-component reaction of an aromatic aldehyde, ethyl acetoacetate and ammonium acetate is described.     

An improved and practical synthesis of 4-fluorobenzaldehyde by halogen-exchange fluorination reaction

A process which can afford a large quantity of 4-fluorobenzaldehyde was developed from halogen-exchange of 4-chlorobenzaldehyde with potassium fluoride in aromatic hydrocarbon solvents in the presence of tetraphenylphosphonium bromide plus polyethylene glycol dimethyl ether. The features of the reaction are discussed.     

改进的Ugi法应用于胺烷基二茂铁衍生物的合成

选择不同的按或酰胺组分, 利用改进的Ugi法合成了一系歹含有烷胺烷基、芳胺烷基或酰胺烷基的二茂铁衍生物, 研究了反应的投料比, 反应底物, 反应温域等因素对反应的影响, 并对反应机理进行了探讨。     

Facile synthesis of sulfur-substituted allenes by a three-component reaction

The three-component reaction of lithium alkylthiolate, 1-alkynylphosphine oxide and aldehyde in THF affords sulfur-substituted allenes in good to excellent yield.     

An effective new synthesis of 2-aminopyrrole-4-carboxylates

Efficient syntheses of 2-aminopyrroles are presented starting from β-dicarbonyl compounds, bromoacetonitrile, and amines. Alkylation of β-dicarbonyl compounds with bromoacetonitrile furnished α-cyanomethyl-β-dicarbonyl compounds. The condensation reaction of α-cyanomethyl-β-dicarbonyl compounds with amines catalyzed by p-TsOH affords the corresponding enamines in good yields. Base catalyzed cyclization via the addition of an amine moiety to the carbon-nitrogen triple bond of nitrile furnished 2-aminopyrroles in high yields.     

A novel aza-Prins-Friedel-Crafts reaction for the synthesis of 4-arylpiperidines

Aldehyde, homoallylic amine and arene undergo smooth cyclization in the presence of BF₃·OEt₂ to afford 4-arylpiperidines in good yields and with high trans-selectivity. This is the first report on the preparation of 4-arylpiperidines via aza-Prins-Friedel-Crafts reaction.     

A facile synthesis of 4-, 5- and 6-chloromethyl-1H-indole-2-carboxylates: replacement of a sulfonic acid functionality by chlorine

Valuable new synthetic intermediates, 4-, 5- or 6-chloromethyl-1H-indole-2-carboxylates, were prepared by the facile elimination of SO₂ from 2-ethoxycarbonyl-1H-indole-4-, 5- or 6-methanesulfonic acids, respectively, easily accessible by Fischer-type indolization.     

One-step synthesis of inherently chiral p-tert-butylcalix[4]azacrown

A one-step procedure is developed to synthesize inherently chiral p-tert-butylcalix[4]azacrown 1 through etherification between p-tert-butylcalix[4]arene and compound 3, which can be amplified to efficiently prepare more inherently chiral calix[4]arenes in ABHH substitution pattern.     

Organocatalyzed enantioselective synthesis of 2-amino-5-oxo-5,6,7,8-tetrahydro-4H-chromene-3-carboxylates

The organocatalyzed enantioselective synthesis of biologically active 2-amino-5-oxo-5,6,7,8-tetrahydro-4H-chromene-3-carboxylate derivatives was achieved using bifunctional cinchona alkaloids as the catalysts. Using quinine thiourea as the catalyst, the tandem Michael addition-cyclization reaction between 1,3-cyclohexanediones and alkylidenecyanoacetate derivatives gives the desired products in high yields (up to 92%) and good ee values (up to 82%).     

Synthesis of orthogonally protected 1,2-diaminopropanoic acids by ring-opening of 3-unsubstituted N-activated aziridine 2-carboxylates with para-methoxybenzylamine: a study of the regioselectivity of the reaction

Orthogonally protected 1,2-diaminopropanoic acids (DAPs) have been synthesised in good yields by the ring-opening of 3-unsubstituted N-activated aziridine 2-carboxylates with para-methoxybenzylamine. The choice of both the N-activating group and ester alkyl group had a significant influence on the ratio of attack at the α or β positions of the aziridine. However, the regiochemical outcome is not predictable.     

Synthesis of Alkyl 5,6-Dialkyl-2-amino-3-cyanopyridine-4-carboxylates

An unusual route has been found for the hydrolysis of 3-amino-1,1-dialkoxy-6,7-dialkyl-4-aryl-3a,4,5,7a-tetrahydro-1H-pyrrolo[3,4-c]pyridine-3a,7a-dicarbonitriles in acidic medium which leads to the formation of alkyl 5,6-dialkyl-2-amino-3-cyanopyridine-4-carboxylates.     

3, 4-二氢嘧啶-2-酮衍生物合成研究进展

综述了近十年来3,4-二氢嘧啶-2-酮衍生物合成的研究进展,包括催化合成、固相合成、微波促进合成及天然产物合成中的一些最新研究进展。     

Choline chloride based eutectic solvent for the efficient synthesis of 2-amino-4H-chromen-4-yl phosphonate derivatives via multicomponent reaction under mild conditions

Synthesis of 2-amino-4H-chromen-4-ylphosphonate derivatives has been accomplished by the one-pot three-component reaction of salicylaldehyde, malononitrile/ethylcyanoacetate and dialkyl phosphites in the presence of reusable deep eutectic solvent (DES) under mild conditions. The advantages of this method are mild reaction conditions, simple work-up procedure, use of DES as a green solvent and an economical protocol for the preparation of important biologically active phosphorus-containing compounds.     

Tandem Heck-Suzuki-Miyaura reaction: Application to the synthesis of constrained analogues of combretastatin A-4

A series of compounds related to combretastatin A-4 has been synthesized by a tandem Heck-carbocyclization/Suzuki coupling process. From various alkynamides and 3,4,5-trimethoxyphenyl boronic acid or the corresponding styryl derivative, (E)-3-arylmethyleneoxindoles (type I) and (EE)-3-alkylideneoxindoles (type II) were efficiently obtained in a stereoselective manner. Factors influencing yield and stereoselectivity are detailed.