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Synthesis of the Ethyl Esters of 4-(3-Pyridyl)- and 4-(4-Pyridyl)-2-oxobutenoic Acids
Abstract
We have developed a method for the synthesis of ethyl 4-(3-pyridyl)- and 4-(4-pyridyl)-2-oxobutenoates by condensation of 3-pyridinecarbaldehyde and 4-pyridinecarbaldehyde monohydrate respectively with ethyl pyruvate, esterifiction of the target acids, and hydrolysis of the corresponding ethyl ester ketals in the presence of FeCl36H2O.
In this study, 1H-imidazol-3-ium trinitromethanide (1) {[HIMI]C(NO2)3} as a green and recyclable catalyst based on nanostructure ionic liquid (NIL) was designed, synthesized, fully characterized by various analysis techniques, and applied as catalyst for the synthesis of 4-amino-1,2-dihydrobenzo[4,5]imidazo[1,2-a]pyrimidine-3-carbonitrile derivatives via one-pot three-component condensation reaction. The reaction tolerates a wide range of electron-donating and electron-withdrawing substituents on aldehydes with malononitrile and 2-aminobenzimidazole at 50 °C under neat conditions. The described reaction is compatible with the green chemistry disciplines and their main advantages are short reaction time, high yields, simplicity of product isolation, and clean reaction profile. Additionally, the NIL catalyst (1) {[HIMI]C(NO2)3} can be readily recovered in the reaction vessel using a mixture of EtOAc/H2O (1:1) and reused for four consecutive runs without a significant loss in catalytic activity. The present study can open up a new and promising insight in the course of rational design, synthesis and applications of nanostructured task-specific ionic liquids (NTSILs) for numerous green purposes.
We have developed a method for the synthesis of ethyl 4-(3-pyridyl)- and 4-(4-pyridyl)-2-oxobutenoates by condensation of 3-pyridinecarbaldehyde and 4-pyridinecarbaldehyde monohydrate respectively with ethyl pyruvate, esterifiction of the target acids, and hydrolysis of the corresponding ethyl ester ketals in the presence of FeCl3·6H2O.
A method was developed for the synthesis of N-[1-(S)-(ethoxycarbonyl)-3-phenylpropyl]alanylproline (enalapril) by reductive alkylation of alanylproline with ethyl 2-oxo-4-phenylbutenoate under the conditions of hydrogenation in the presence of palladium black and 1.6% Pd/C. The yield of enalapril amounted to 65%. With the ethyl ester of the α-oxo acid the diastereoselectivity of formation of the S,S,S-diastereomer was higher than with the saturated synthon. It is assumed that with ethyl 2-oxo-4-phenylbutenoate as synthon a conformationally restricted surface complex is formed between the unsaturated synthon and the active centers of the catalyst. During reductive alkylation of alanylproline by ethyl 2-oxo-4-(2-thienyl)butenoate poisoning of the catalyst occurs.
A number of analogues of diaryl dihydropyrazole-3-carboxamides have been synthesized. Their activities were evaluated for appetite suppression and body weight reduction in animal models. Depending on the chemical modification of the selected dihydropyrazole scaffold, the lead compounds--the bisulfate salt of (+/-)-5-(4-chlorophenyl)-1-(2,4-dichlorophenyl)-4,5-dihydro-1H-pyrazole-3-carboxylic acid morpholin-4-ylamide 26 and the bisulfate salt of (-)-5-(4-chlorophenyl)-1-(2,4-dichlorophenyl)-4,5-dihydro-1H-pyrazole-3-carboxylic acid morpholin-4-ylamide 30--showed significant body weight reduction in vivo, which is attributed to their CB1 antagonistic activity and exhibited a favorable pharmacokinetic profile. The molecular modeling studies also showed interactions of two isomers of (+/-)-5-(4-chlorophenyl)-1-(2,4-dichlorophenyl)-4,5-dihydro-1H-pyrazole-3-carboxylic acid morpholin-4-ylamide 9 with CB1 receptor in the homology model similar to those of N-piperidino-5-(4-chlorophenyl)-1-(2,4-dichlorophenyl)-4-methyl-3-pyrazole-carboxamide (rimonabant) 1 and 4S-(-)-3-(4-chlorophenyl)-N-methyl-N'-[(4-chlorophenyl)-sulfonyl]-4-phenyl-4,5-dihydro-1H-pyrazole-1-carboxamidine (SLV-319) 2.
New way for the preparation of 4-phenyl-2-oxobutyric acid ethyl ester 1 has been elaborated. The four-steps synthesis from ethyl pyruvate involves the consecutive condensation of ethyl pyruvate with benzaldehyde, hydrogenation of benzylidenepyruvic acid sodium salt 2a to 4-phenyl-2-hydroxybutyric acid 3 on Ni catalysts, esterification of 3 and oxidation of the ester to 1 with CrO3.
A variety of acetonides and acetals were efficiently cleaved using CuCl2.2H2O in MeCN. The method was effectively used in synthesis of chiral diols which are important in asymmetric synthesis.
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