Synthesis of ursodeoxycholic acid by electrochemical stereoselective reduction of 7-ketolithocholic acid in aprotic solvents

A novel method of producing ursodeoxycholic acid was developed through electrochemical stereoselective reduction of 7-ketolithocholic acid (7K-LCA) in a undivided electrolytic cell and aprotic solvents as electrolyte. Five aprotic solvents were investigated as electrolytes, the simple structure of dimethyl sulfoxide (DMSO) and N,N-dimethylformamide (DMF) were easily attacked by chloride ions and undergo nucleophilic reactions, resulting in no target reactions. The structure of hexamethylphosphoric triamide (HMPA) and 1,3-methyl-3,4,5,6-tetrahydro-2 (1H) -pyrimidinone (DMPU) is relatively complex, but chloride ions can still attack them, and it was easier for 7K-LCA to directly undergo a reduction reaction under the action of electric current, because of the small steric hindrance of chenodeoxycholic acid (CDCA), 7K-LCA was stereoselectively reduced to CDCA. Due to the stable structure of the five-membered imidazole ring of 1,3-dimethyl-2-imidazolidinone (DMI), 7K-LCA undergoes two nucleophilic and a "Walden inversion", thereby stereoselective reduction of 7K-LCA to UDCA. In DMI, the highest conversion rate of 7K-LCA was 58.3%, the yield of UDCA was 34.9%, ee value was 100%. Linear sweep voltammetry was used to explore the electrochemical behavior of the reaction, and the electrolysis results were consistent with the linear sweep voltammetry. The product was characterized by using IR, 1H NMR and 13C NMR, it confirm the product was UDCA. The method developed in this paper provides a relatively environmentally friendly and low-consumption method for large-scale production of ursodeoxycholic acid, and provides a valuable reference for the asymmetric electrochemical reduction of ketone groups.

Спектрально-люминесцентные свойства разнолигандных комплексных соединений европия(III) c o-метоксибензойной кислотой и фосфорсодержащими нейтральными лигандами

The spectral and luminescent properties of complex compounds of europium (III) with o-methoxybenzoic acid and island-containing phosphorus-containing neutral ligands of the composition Eu (MOBA) 3 • 3Н2О and Eu (MOBA) 3 • L, where MOBA is o-methoxybenzoic acid, D is studied (hexamethylphosphoric triamide), tppo (triphenylphosphine oxide), Et6pa (hexaethylphosphotriamide). It was found that the excitation energy is transferred to the europium ion both from the levels of o-methoxybenzoic acid and from the levels of phosphorus-containing neutral ligands.The electronic absorption spectra, the luminescence excitation spectra, and the Stark structure of 5D0-7Fj (j = 0-2) electronic transitions in the luminescence spectra of mixed-ligand complex europium (III) complex o-methoxybenzoates are analyzed. Europium (III) methoxybenzoate with triphenylphosphine oxide has the highest luminescence intensity.

Разнолигандные комплексные соединения европия (III) с o-метоксибензойной кислотой и фосфорсодержащими нейтральными лигандами

The luminescent coordination multi-ligand compounds of europium (III) with o-methoxybenzoic acid and island-containing phosphorus-containing neutral ligands of the composition Eu (MOBA) 3 • 3Н2О and Eu (MOBA) 3 • L, where MOBA is o-methoxybenzoic acid, D is hmpa (D hexamethylphosphoric triamide), tppo (triphenylphosphine oxide), Et6pa (hexaethylphosphotriamide). The composition, structure, and thermal properties of complex multi-ligand compounds of europium (III) were studied. It was shown that during thermolysis, detachment of a neutral ligand molecule occurs in one stage with an endothermic effect, complex compounds are stable up to 280 С.Based on the data of IR spectroscopy, it was found that in the europium (III) o-methoxybenzoates, the o-methoxybenzoic acid is coordinated to the europium (III) o-methoxybenzoic ion in a bidentate manner. The low luminescence intensity of multi-ligand europium (III) compounds is explained by the inefficient transfer of electronic excitation energy from o-methoxybenzoic acid and phosphorus-containing neutral ligands to the europium ion.

HMPA-Catalyzed Transfer Hydrogenation of 3-Carbonyl Pyridines and Other N-Heteroarenes with Trichlorosilane

A method for the HMPA (hexamethylphosphoric triamide)-catalyzed metal-free transfer hydrogenation of pyridines has been developed. The functional group tolerance of the existing reaction conditions provides easy access to various piperidines with ester or ketone groups at the C-3 site. The suitability of this method for the reduction of other N-heteroarenes has also been demonstrated. Thirty-three examples of different substrates have been reduced to designed products with 45–96% yields.

Synthesis of hydrosilanes via Lewis-base-catalysed reduction of alkoxy silanes with NaBH4

Hydrosilanes were synthesized by reduction of alkoxysilanes with BH3 in the presence of hexamethylphosphoric triamide (HMPA) as a Lewis-base catalyst. The reaction was also achieved using an inexpensive and easy-to-handle handled hydride source NaBH4, which reacted with EtBr as a sacrificial reagent to form BH3in situ.