Vol 55, No 9 (2019)

The review generalizes published data on the synthesis of atropisomeric arylimide, porphyrin, and benzimidazole derivatives, helically chiral compounds (helicenes), and axially chiral molecules.

The condensation of 1-phenoxy-3-(propylsulfanyl)propan-2-ol with formaldehyde and secondary aliphatic and heterocyclic amines afforded new aminomethoxy derivatives of 1-phenoxy-3-(propylsulfanyl)- propane in 69–77% yields. The product structure was confirmed by elemental analyses and IR and ¹H and ¹³C NMR spectra. The synthesized compounds were assayed as antiseptics against bacteria and fungi and were shown to be more efficient antimicrobial agents than those currently used in medicine.

Oxidative chlorination of 6-methyluracil-5-carbaldehyde oxime in a two-phase system gave 7V-hydroxy-6-methyluracil-5-carboximidoyl chloride, and its bromination afforded ipso-substitution products, 5-bromo-6-methyluracil and 5,5-dibromo-6-hydroxy-6-methyl-5,6-dihydrouracil. The reaction of the title compound with acetic anhydride led to the formation of 6-methyluracil-5-carbonitrile or O-acetyl derivative, depending on the temperature. 7V-Hydroxy-6-methyluracyl-5-carboximidoyl chloride reacted with acetic acid at 100°C or with potassium iodide in boiling acetone to produce uracil-5-hydroxamic acid which was converted with high yields into the corresponding methyl ester and hydroximic acid amide. Quaternary ammonium salts were obtained by reactions of N-hydroxy-6-methyluracil-5-carboximidoyl chloride with pyridine and 1-methyl-1H-imidazole.

Methods have been developed for the synthesis of unsaturated ketones of the dihydropyran series via aldolization-crotonization of 3,4-dihydro-2H-pyran-2-carbaldehyde with some unsaturated ketones. Among the proposed methods, the optimal were reactions carried out in 20% alcoholic sodium hydroxide at room temperature, which ensured higher selectivity, high yield (85-95%) of the target products, and minimization of side processes. The obtained unsaturated ketones were subjected to various chemical transformations involving the side-chain double bond, and their new derivatives were synthesized. In particular, the oxidation of unsaturated ketones with 28% hydrogen peroxide gave the corresponding epoxy ketones which reacted with secondary amines to afford amino alcohols.

Some peculiar features of two most commonly used catalytic systems (Cul and CuSOVsodium ascorbate) controlling the regioselectivity of 1,3-dipolar cycloaddition of azides to terminal alkynes have been studied. Their potentialities, main disadvantages, and limitations have been demonstrated by a number of examples, including reactions of low-molecular-weight azides and alkynes containing heterocyclic substituents. The possibility of using novel reagents in click reactions is discussed.

New 7-aryl(hetaryl)-9,10-dihydro-7H-cyclopenta[b][1,7]phenanthrolin-8(11H)-ones have been synthesized by three-component condensation of quinolin-5-amine with cyclopentane-1,3-dione and aldehydes of the aromatic and heteroaromatic series.

The mechanism of sodium methoxide-catalyzed transesterification of diethyl carbonate with metha-nol to dimethyl carbonate has been studied by DFT quantum chemical calculations using B3LYP functional. Ethoxy groups in the substrate are replaced successively through four-coordinate carbon intermediates which undergo decomposition. Sodium methoxide with carbonates forms pre-reaction complexes where the sodium cation is coordinated to the carbonate fragment. These complexes are characterized by enhanced electron-donating power of the methoxy fragment and increased electron-withdrawing power of the carbonate fragment, which favors the transesterification process.

—A procedure was developed for the synthesis of 1-hydrazinyl-3-arylamino-5,6,7,8-tetrahydroisoquinoline- 4-carbonitriles via recyclization of the pyridine ring in 3-amino-2-aryl-1-sulfanylidene-1,2,5,6,7,8- hexahydroisoquinoline-4-carbonitriles by the action of hydrazine hydrate. The recyclization products were converted to new heterocyclic systems, 7,8,9,10-tetrahydro[1,2,4]triazolo[3,4-a]isoquinolines and 1-(3,5-dimethyl- 1H-pyrazol-1-yl)-5,6,7,8-tetrahydroisoquinolines, by reactions with triethyl orthoformate and acetylacetone, respectively. Treatment of 1-hydrazinyl-3-arylamino-5,6,7,8-tetrahydroisoquinoline-4-carbonitriles with sodium azide in acetic acid gave 1-azido-3-arylamino-5,6,7,8-tetrahydroisoquinoline-4-carbonitriles, and azide–tetrazole isomerism of the latter was studied. The state of the azide–tetrazole equilibrium was found to depend on the solvent polarity and substituent nature in the arylamino group. The structure of 5-(2-methoxyanilino)- 7,8,9,10-tetrahydro[1,2,4]triazolo[3,4-a]isoquinoline-6-carbonitrile was confirmed by X-ray analysis, and intermolecular hydrogen bonds were detected in its crystal structure. The synthesized compounds were evaluated for antimicrobial activity.

A synthetic approach is described for the transformation of R-(-)-carvone to methyl (2Z,5S,6E)-5-[(tert-butoxycarbonyl)amino]-2,6-dimethyl-7-(2-methyl-1,3-thiazol-4-yl)hepta-2,6-dienoate, the key building block for the convergent synthesis of the known antitumor macrolactam ixabepilone. The synthetic sequence includes 10 stages, where the key stage is Curtius rearrangement. Optimal conditions have been found for that rearrangement.

A new strategy has been proposed for the synthesis of 9-arylhexahydroacridine-1,8-diones by three-component condensation of aromatic aldehydes with 5,5-dimethylcyclohexane-1,3-dione and ammonium acetate in ethanol, using nontoxic, available, and inexpensive phosphate fertilizers [monoammonium phosphate (MAP), diammonium phosphate (DAP), and triple super phosphate (TSP)] as heterogeneous catalysts. Notable advantages of the proposed method include operational simplicity, low cost of the reactants, favorable environmental profile, good yield, short reaction time, recovery and reuse of the catalyst, and valorization of Moroccan natural phosphate.

New substituted 5,6-dihydro[1,2,4]triazolo[4,3-a][1,3,5]triazines were synthesized by cyclocondensation of N-alkyl(aryl)-N′-(4H-1,2,4-triazol-3-yl)ethan- and -propanimidamides with benzaldehyde or ethyl methyl ketone in the presence of p-toluenesulfonic acid in 1,4-dioxane under reflux. The reaction tolerated a broad substrate scope and provided good yields (43–64%). The structure of the newly synthesized compounds was confirmed by elemental analyses and IR, ¹H and ¹³C NMR, and mass spectra.

New and efficient synthetic approaches to phenothiazine derivatives have been developed on the basis of reactions of 1-(10H-phenothiazin-2-yl)ethanone hydrazone with isothiocyanates and hydrazonoyl chlorides under conventional thermal heating and microwave irradiation. The structures of the newly synthesized compounds have been confirmed by elemental analyses and spectroscopic data.

Potassium fluoride-modified clay collected from the region of Agadir (Morocco) was used as a hetaerogeneous catalyst in the one-pot synthesis of 3,4-dihydropyrimidine-2(1H)-one derivatives via the Biginelli reaction. The products were obtained with excellent yields (88–98%). The catalyst was characterized X-ray powder diffraction, Fourier-transform IR spectroscopy, scanning electron microscopy, differential thermal analysis, thermogravimetry, and Brunauer–Emmett–Teller (BET) analysis. Plausible reaction mechanisms for both reactions have been proposed. The catalyst can be recycled five times without loss of catalytic activity.

Coupling of previously synthesized chiral building blocks via Yamaguchi esterification has been studied with the goal of obtaining epothilone D isosteres. Some peculiar features of the Yamaguchi esterification stage have been revealed, which are related to the reactivity and molecular structure of the initial acid and alcohol components.