Direct electrophilic acylation of n-substituted pyrazoles by anhydrides of carboxylic acids

A simple, convenient and scalable approach to 1-substituted 4-acylpyrazoles through direct acylation of pyrazoles by anhydrides of aliphatic, aromatic and fluorinated carboxylic acids in the presence of concentrated sulfuric acid as a catalyst is described. Target ketones were obtained in 41-86% isolated yields in high purity without laborious purification. The scope and limitations of the method are discussed. © 2013 Georg Thieme Verlag Stuttgart New York

Direct electrophilic acylation of n-substituted pyrazoles by anhydrides of carboxylic acids

A simple, convenient and scalable approach to 1-substituted 4-acylpyrazoles through direct acylation of pyrazoles by anhydrides of aliphatic, aromatic and fluorinated carboxylic acids in the presence of concentrated sulfuric acid as a catalyst is described. Target ketones were obtained in 41-86% isolated yields in high purity without laborious purification. The scope and limitations of the method are discussed. © 2013 Georg Thieme Verlag Stuttgart New York

Direct bromination of ethyl 5-alkylthiophene-2-carboxylates

Approaches to brominated thiophene-2-carboxylic acids by electrophilic bromination of the corresponding acids and esters were compared and investigated. A synthetic route was developed involving direct bromination of ethyl 5-alkylthiophene-2-carboxylates followed by saponification of the resulting ethyl 5-alkyl-4-bromothiophene-2-carboxylates. The key bromination step is selective in dichloromethane solution at 0-5 °C and furnishes the corresponding ethyl 5-alkyl-4-bromothiophene-2-carboxylates in excellent yields. No migration or isomerization of the alkyl substituents was observed. © Georg Thieme Verlag Stuttgart New York

Modified method for the synthesis of isomeric N-substituted (1H-pyrazolyl)propane-1,3-diones

The condensation reaction of isomeric N-substituted (1H-pyrazol-4-yl) ethanones with the ethyl esters of pyrazole carboxylic acids and fluoroacetic acids has been studied using NaH as the base. Under optimized conditions, it proved to be a convenient and preparative method for the synthesis of N-substituted (1H-pyrazolyl)propane-1,3-diones and (1H-pyrazolyl)-4- polyfluorobutane-1,3-diones. © 2011 Springer Science+Business Media, Inc

Direct bromination of ethyl 5-alkylthiophene-2-carboxylates

Approaches to brominated thiophene-2-carboxylic acids by electrophilic bromination of the corresponding acids and esters were compared and investigated. A synthetic route was developed involving direct bromination of ethyl 5-alkylthiophene-2-carboxylates followed by saponification of the resulting ethyl 5-alkyl-4-bromothiophene-2-carboxylates. The key bromination step is selective in dichloromethane solution at 0-5 °C and furnishes the corresponding ethyl 5-alkyl-4-bromothiophene-2-carboxylates in excellent yields. No migration or isomerization of the alkyl substituents was observed. © Georg Thieme Verlag Stuttgart New York

Modified method for the synthesis of isomeric N-substituted (1H-pyrazolyl)propane-1,3-diones

The condensation reaction of isomeric N-substituted (1H-pyrazol-4-yl) ethanones with the ethyl esters of pyrazole carboxylic acids and fluoroacetic acids has been studied using NaH as the base. Under optimized conditions, it proved to be a convenient and preparative method for the synthesis of N-substituted (1H-pyrazolyl)propane-1,3-diones and (1H-pyrazolyl)-4- polyfluorobutane-1,3-diones. © 2011 Springer Science+Business Media, Inc

Improved synthesis of 1H-pyrazole-4-carbaldehyde

A simple and convenient two-step method for the synthesis of the title compound 1 was developed using N-protected 4-pyrazolilmagnesium bromide 9 as a key intermediate. Laborious procedures for purification or isolation of target compound are not required, therefore, up to 20g of 1 could be obtained in a single run. © 2011 Taylor & Francis Group, LLC

Convenient modification of the Leimgruber-Batcho indole synthesis: Reduction of 2-nitro-p-pyrrolidinostyrenes by the FeCl3-activated carbon-N2H4H2O system

A new catalytic system containing ferric chloride, activated carbon, and hydrazine has been proposed for the reductive cyclization of β-dialkylamino-2-nitrostyrenes to give the corresponding indoles (Leimgruber-Batcho synthesis). Various substituted indoles may be obtained in high yield under these conditions. © 2011 Springer Science+Business Media, Inc

Improved synthesis of 1H-pyrazole-4-carbaldehyde

A simple and convenient two-step method for the synthesis of the title compound 1 was developed using N-protected 4-pyrazolilmagnesium bromide 9 as a key intermediate. Laborious procedures for purification or isolation of target compound are not required, therefore, up to 20g of 1 could be obtained in a single run. © 2011 Taylor & Francis Group, LLC

Synthesis, X-ray structure and luminescent properties of Sm3+ ternary complex with novel heterocyclic β-diketone and 1,10-phenanthroline (Phen)

A new neutral ternary samarium complex Sm(Phen)HL3 in which Phen is 1,10-phenanthroline and HL is (1,3-bis(1,3-dimethyl-1H-pyrazol-4-yl)-1,3- propanedione) was synthesized. Molecular structure of this complex was determined by X-ray diffraction. Under UV-light this complex is demonstrated bright red luminescence (λmax=647 nm), which was corresponding to the electric dipole 4G5/2→6H 9/2 transition in Sm3+ ion. UV-absorption, excitation and emission spectra of the title compound were investigated. © 2011 The Chinese Society of Rare Earths