Volume 55, Nº 6 (2019)

The catalytic efficiencies of palladium(0) and copper(I) complexes in the amination of 2-bromopyridine and its fluorine-containing derivatives with (1-adamantyl)methanamine and 2-(1-adamantyloxy)ethanamine were compared. Both types of catalytic systems were shown to be applicable for the preparation of the corresponding N-pyridyl derivatives from 3- and 5-fluoro- and 4-, 5-, and 6-trifluoromethyl-2-bromopyridines. DavePhos was found to be the most efficient ligand in the Pd(0)-catalyzed reactions; however, the reactions with 2-bromo-4-(trifluoromethyl)pyridine and 2-bromo-5-(trifluoromethyl)pyridine were accompanied by formation of a considerable amount of the diarylation product. The diarylation process was significantly suppressed in the presence of copper(I) complexes.

Purine and 2-aminopurine conjugates with N-(4-aminobenzoyl)-(S)-glutamic acid connected to C⁶ of the purine system either directly or through an aminoethyl linker have been synthesized by nucleophilic substitution of chlorine in 6-chloropurine and 2-amino-6-chloropurine. 2-Aminopurine conjugate with 4-aminobenzoic acid linked through a glycine residue has also been obtained. Testing of the synthesized compounds for tuberculostatic activity in vitro has revealed a moderate activity of methyl 4-[2-(2-aminopurin-6-ylamino)-acetyl]amino}benzoate.

Transesterification of dialkyl carbonates with 2,2,3,3-tetrafluoropropan-1-ol in the presence of various bases leads to the formation of mixtures of bis(2,2,3,3-tetrafluoropropyl) carbonate and alkyl 2,2,3,3-tetrafluoropropyl carbonate. The best catalyst for the synthesis of alkyl 2,2,3,3-tetrafluoropropyl carbonates was found to be tetramethylammonium hydroxide which ensured 81% selectivity for methyl 2,2,3,3-tetrafluoropropyl carbonate, the conversion of dimethyl carbonate being 50%. Lithium alkoxides showed a comparable catalytic efficiency.

The structure of 6-polyfluoroalkyl-2-thiouracils and reactivity of nucleophilic centers in their molecules were analyzed by quantum chemical calculations. According to the experimental data, methylation of 6-polyfluoroalkyl-2-thiouracils with methyl iodide initially gives 2-methylsulfanyl-substituted pyrimidin-4-one and then S,N³- and S,O-dimethyl derivatives. The optimal conditions for the selective formation of the S, N³- isomer were heating in tert-butyl alcohol in the presence of cesium carbonate as a base. Ethylation of 6-polyfluoroalkyl-2-thiouracils afforded approximately equal amounts of S,N³- and S,O-dimethyl derivatives. S,N³-Dimethyl-substituted pyrimidines in boiling ethanol in the presence of potassium carbonate were converted into uracil potassium salts as a result of nucleophilic substitution of the methylsulfanyl group by ethoxy and subsequent dealkylation of the latter.

Alkaline hydrolysis of 1-(2,3-dihydro-1,4-benzodioxin-6-yl)cyclopentane-1-carbonitrile gave the corresponding carboxylic acid which was converted to carbonyl chloride, and the latter reacted with N, N-di-alkylalkane-α,ω-diamines and dialkylaminoalkanols to afford new amino amides and amino esters which were isolated as hydrochlorides. Anticonvulsant activity of the synthesized compounds was studied.

The review summarizes recent advances in the use of homochiral metal—organic frameworks (MOFs) in asymmetric catalysis of organic reactions.

Fragmentation of N, N-dialkyl-7-[alkyl and 2-(vinyloxy)ethyl]-2,7-dihydrothiopyrano[2,3-b]pyrrol-6-amines under electron impact (70 eV) and chemical ionization (methane as reactant gas) has been studied. The electron impact ionization of these compounds gives rise to stable molecular ions which decompose according to two main pathways. The major pathway involves cleavage of the N⁷—C_Alk bond with elimination of the alkyl radical. The minor pathway is expulsion of alkyl radical from the amino nitrogen atom in the 6-position. The chemical ionization of 2,7-dihydrothiopyrano[2,3-b]pyrrol-6-amines characteristically involves protonation and electrophilic addition processes with the most abundant ion being [M + H]⁺.

Six regioisomeric nonracemic dimethylphenyl glycerol ethers were synthesized by asymmetric dihydroxylation of the corresponding allyl dimethylphenyl ethers. The enantioselectivity of the reaction with o-methyl derivatives was lower (down to 34% ee) than with m-methylphenyl ethers (up to 86% ee). Enantiomeric 3-(3,4-dimethylphenoxy)propane-1,2-diols were used to obtain enantiomerically pure physiologically active amino alcohols and their derivatives.

A series of novel sulfonamides containing a 2-amino-1,3-thiazole fragment have been synthesized using a simple and efficient method under solvent-free conditions. The obtained N-(4-sulfamoyl-1,3-thiazol-2-yl)-4-nitrobenzamides were evaluated for their antibacterial activity against S. aureus and E. coli, and in silico ADME prediction was performed to find biological behavior.

A novel fluorescent probe, DHMP {7-(dibutylamino)-3-methyl-1H,3′H-spiro[chromeno[2,3-c]pyrazole-4,1′-[2]benzofuran]-3′-one} was designed and synthesized by condensation of 2-[4-(dibutylamino)-2-hydroxybenzoyl]benzoic acid with 5-methyl-2,4-dihydropyrazol-3-one. The ultraviolet absorption and fluorescence emission spectra of DHMP showed a clear pH dependence and highly selective and sensitive response to copper(II) ions in aqueous medium. The detection limit of Cu²⁺ was estimated at 9.05 × 10⁻⁸ M.

Heterocyclization of 5,5-difluoro- and 5,5,5-trifluoro-2,4-dioxopentanal dimethyl acetals with amidines in the presence of 4 equiv of triethyl borate afforded 2-substituted 6-(difluoromethyl)- and 6-(trifluoromethyl)pyrimidine-4-carbaldehyde dimethyl acetals in high yields.

An efficient synthetic approach to phenazone derivatives containing a 1,2,4-triazine or pyridine fragment has been proposed on the basis of successive nucleophilic substitution of hydrogen (\({\rm{S_N^H}}\)) in 1,2,4-triazine 4-oxides and aza-Diels-Alder reaction with norbornadiene as dienophile.

Previously unknown 4-(polyfluoroacylmethyl)-substituted pyrimidines were synthesized by reaction of 1,5-bis(polyfluoroalkyl)-1,3,5-triketones with amidines.

The second author should be Chen-Fu Liu.