Showing papers in "Russian Journal of Organic Chemistry in 2001"

Synthesis and Reactivity of Carbohydroximoyl Azides: I. Aliphatic and Aromatic Carbohydroximoyl Azides and 5-Substituted 1-Hydroxytetrazoles Based Thereon

Abstract: Chlorination of 1-hydroxyiminopentane gave 1-chloro-1-nitrosopentane which reacted with sodium azide in DMF to form pentanohydroximoyl azide. The azidation of benzohydroximoyl chlorides was always accompanied by decomposition to benzonitriles. Treatment of carbohydroximoyl azides in ether with gaseous hydrogen chloride afforded 5-butyl- and 5-aryl-1-hydroxytetrazoles which reacted with acetic anhydride to form the corresponding acetates.

Some Specific Features of Acid Nitration of 2-Substituted 4,6-Dihydroxypyrimidines. Nucleophilic Cleavage of the Nitration Products

Abstract: The nitration of 2-substituted 4,6-dihydroxypyrimidines in concentrated sulfuric acid yields the corresponding 5,5-dinitro derivatives. When the substituent in position 2 is an alkyl group, the nitration occurs both at position 5 and at the α-carbon atom of the side chain. Hydrolysis of 2-substituted 4,6-dihydroxy-5,5-dinitropyrimidines leads to formation of 1,1-diamino-2-R-2-nitroethylene derivatives. 1,1-Diamino-2,2-dinitro-ethylene was obtained by nitration of 4,6-dihydroxy-2-methylpyrimidine and subsequent hydrolysis of 4,6-dihydroxy-5,5-dinitro-2-(dinitromethylene)-2,5-dihydropyrimidine.

Efficient Oxidation of Sulfides to Sulfoxides and of Thiols to Disulfides with Aqueous HIO3

Abstract: Oxidations of thiols to disulfides and of sulfides to sulfoxides under mild conditions in organic media are of practical importance for organic synthesis. Taking into account that thiols and sulfides are easily oxidizable and may thus be overoxidized, extensive studies have been carried out to develop methods for controlled oxidation of these compounds [1312]. The known oxidants are not free from disadvantages, including difficult accessibility [4, 8], methods of preparation [2, 8], long reaction time [5, 12], laborious treatment of the reaction mixture [4, 12], and high toxicity [1]. We have found that aqueous HIO3 may be very effective reagent for the transformation of thiols into disulfides, ensuring high yields of the products and requiring no organic solvent (Table 1). Aqueous HIO3 was also found to effectively oxidize sulfides to the corresponding sulfoxides. These reactions are carried out by heating the reactants on a steam bath, and sulfoxides are formed in excellent yields (Table 1). It should be noted that thiols and sulfides having double CIC bonds could not be oxidized with aqueous HIO3 with the same selectivity; therefore, this procedure cannot be recommended for oxidation of unsaturated thiols and sulfides. Table 2 compares the efficiency of the proposed procedure with some published results [7, 8, 11]. The oxidation of sulfides and thiols with aqueous HIO3 is superior to the other methods, for it utilizes cheap and accessible reagents, occurs under mild conditions, and ensures good yields and easy isolation of the products. A mixture of 1 mmol of thiol or sulfide and 0.25 g of aqueous HIO3 (54 wt %) was agitated at room ____________ * The original article was submitted in English. temperature using a magnetic stirrer or heated on a steam bath for a time specified in Table 1. The progress of the reaction was monitored by TLC or GLC. When the reaction was complete, 5 ml of CH2Cl2 and 0.5 g of Na2S2O3 were added, and the mixture was stirred for 15 min and filtered. The filtrate was dried over anhydrous MgSO4 and evaporated, and the residue was purified by column chromatography on silica gel. Reagents from Merck, Fluka, BDH, and Aldrich were used. The products were isolated and purified by chromatographic methods and were identified by comparing their physical properties (melting or boiling points and refractive indices) and IR and

Fluorocontaining 1,3-Dicarbonyl Compounds in the Synthesis of Pyrimidine Derivatives

Abstract: Hexafluoroacetylacetone reacts with urea (thiourea) to yield respectively 4,6-bis(hydroxy)-4,6-bis(trifluoromethyl)hexahydropyrimidin-2-one(thione). The dehydration of the products and also reaction of nonsymmetrical fluoroalkyl-containing 1,3-diketones with urea (thiourea) afford substituted pyrimidines. The condensation of fluorinated 3-oxoesters and 1,3-diketones with benzaldehyde and urea (thiourea) results in 5-alkoxycarbonyl(acyl)-4-hydroxy-2-oxo(thioxo)-6-phenyl-4-fluoroalkylhexahydropyrimidines that on dehydration furnish 5-alkoxycarbonyl(acyl)-2-oxo(thioxo)-4-phenyl-6-fluoroalkyltetrahydropyrimidines. Ethyl 7-nonafluorobutyl-5-phenyl-2,3-dihydrothiazolo[3,2-a]pyrimidine-6-carboxylate hydrobromide forms in reaction of dibromoethane with ethyl ether of 2-thioxo-4-phenyl-6-nonafluorobutyltetrahydropyrimidine.

Tributylstannyl Aryl Selenides as Efficient Arylselenating Agents in the Synthesis of Seleno Esters

Abstract: Tributyltin aryl selenides are convenient and highly efficient arylselenating agents in reactions with acyl chlorides. The activity of acetic anhydride is considerably lower but it can be involved into the arylselenation reaction in the presence of PdCl2(PPh3)2 or boron trifluoride etherate as catalysts.

1,3,4,6-Tetracarbonyl Compounds: IV. Reaction of 3,4-Dihydroxy-2,4-hexadiene-1,6-diones with Hydrazine and Arylhydrazines

Abstract: Reactions of 1,6-disubstituted 3,4-dihydroxy-2,4-hexadiene-1,6-diones with hydrazine hydrate or hydrochloride afforded heterocyclization products, 3,3'-bipyrazoles. The chemoselective reaction of 1,6-diaryl-3,4-dihydroxy-2,4-hexadiene-1,6-diones with arylhydrazines gave rise to 1,1',5,5'-tetraaryl-3,3'-bipyrazoles and 1,5-diaryl-3-aroylacetylpyrazoles. The specific structural features of the pyrazole derivatives obtained are discussed. Some pyrazoles show bacteriostatic and antileukemic activity.

Nucleophilic Substitution at a Four-Coordinate Sulfur Atom: VI. Reactivity of Oximate Ions

Abstract: The kinetics of the reaction of oximate ions with 2,4-dinitrophenyl p-toluenesulfonate, 4-nitrophenyl p-toluenesulfonate, diethyl 4-nitrophenyl phosphate, and ethyl 4-nitrophenyl ethylphosphonate in H2O-DMSO mixtures (0 to 95 vol % of DMSO) cannot be described in terms of a single Bro/nsted equation. Regardless of the nature of the reaction center and leaving group, both in water and in 80% DMSO fast leveling of the reactivity of oximate ions is observed, the α-effect decreases at pKa ≥ 9.0 and disappears at pKa ≥ 12.0 owing to difference in the solvation of weakly (pKa ≤ 9.0) and strongly basic (pKa ≥ 9.0) oximate ions rather than to change of the transition state. Just unfavorable solvation effects are responsible for the fact that the limiting nucleophilic reactivity of oximate ions (as typical α-nucleophiles) is not higher than the reactivity of strongly basic alkoxide ions.

Synthesis and reactivity of carbohydroximoyl azides: II. 4-substituted 1,2,5-oxadiazole-3-carbohydroximoyl azides and 1-hydroxy-5-(4-R-1,2,5-oxadiazol-3-yl)tetrazoles

Abstract: Diazotization of 4-amino-1,2,5-oxadiazole-3-carbohydroximoyl chloride gave 4-[chloro(hydroxyimino) methyl]-1,2,5-oxadiazole-3-diazonium salt Treatment of the latter with NaN3 afforded 4-azido-1,2,5-oxadiazole-3-carbohydroximoyl chloride, and the reaction with NaNO2 yielded 2-cyano-2-hydroxyiminoacetohydroximoyl chloride By oxidation of 4-amino-1,2,5-oxadiazole-3-carbohydroximoyl azide with KMnO4 in hydrochloric acid 4,4′-dicyano-3,3′-azobis(1,2,5-oxadiazole) was obtained Azidation of 1,2,5-oxadiazole-3-hydroximoyl chlorides resulted in formation of the corresponding 1,2,5-oxadiazole-3-carbohydroximoylazides which were brought into reactions with acetic anhydride and acetyl chloride Decomposition of 4-azido-1,2,5-oxadiazole-3-carbohydroximoyl azide gave 4-azido-1,2,5-oxadiazole-3-carbonitrile; treatment of the same compound with gaseous hydrogen chloride in ether afforded 1-hydroxy-5-(4-azido-1,2,5-oxadiazole-3-yl)tetrazole which was converted into the corresponding acetate by reaction with acetic anhydride

Aminoazoles in Heterocycles Synthesis: II. * Trifluoromethyl-containing Diketones in the Synthesis of Pyrazolo(1,5-a)pyrimidines

Abstract: A regioselective synthesis was carried out of 7-trifluoromethylpyrazolo[1,5-a]pyrimidines by reaction of 3(5)aminopyrazoles with 1,3-diketones containing CF3 group. The characteristic chemical shifts were established for C5 and C7 atoms of the pyrimidine ring and of substituents thereof in the 1H, 13C, and 19F NMR spectra of pyrazolo[1,5-a]pyrimidines.

4-Functionally Substituted 3-Heterylpyrazoles: III. 3-Aryl(heteryl)pyrazole-4-carboxylic Acids and Their Derivatives

Abstract: 3-Aryl(heteryl)-4-formylpyrazoles were cleanly oxidized by potassium permanganate in water-pyridine medium to afford in high yield 3-aryl(heteryl)pyrazole-4-carboxylic acids, that were further converted into the corresponding chlorides and amides.

Heterylation of 3-R1-5-R2-1,2,4-Triazoles with Derivatives of 3,5-Dinitro-1,2,4-Triazole

Abstract: Heterylation of 3-R1-5-R2-1'2'4-triazoles (pKa 3-12) with N-alkyl-, N-alkenyl-, N-alkoxy-carbonyl-, N-oxoalkyl-, N-nitroxyalkyl, N-nitroaminoalkyl-3'5-dinitro-1'2'4-triazoles results insubstitution of a nitro group in 5 position of the dinitro compound yielding 1-R-methyl-3-nitro-5-(3-R1-5-R2-1,2,4-triazolyl)-1,2,4-triazoles. The side processes: Hydroxide-ion attack on C5 and (or) N1 of the ring both in the substrate and in the target compound afford 1-R-methyl3-nitro-1,2,4-triazol-5-ones, 3,5-dinitro-1,2,4-triazole and NH-acids of N-C-bitriazole series. Optimal reaction media are aprotic dipolar substances, and for compounds prone to heterolysis ethyl acetate-water systems. The azole pKa is the decisive factor controlling the composition and the ratio of reaction products. The process is promising for azoles with pKa > 5, and the optimal range of pKa is 8-10.

Synthesis and Properties of 2,2-Dichlorovinyl Trifluoromethyl Ketone

Abstract: Highly reactive 2,2-dichlorovinyl trifluoromethyl ketone was synthesized. Its reactions with N,N-and N,S-nucleophiles gave 1,3-thiazine, pyrazole, and imidazole derivatives containing a trifluoromethyl substituent.

Tributyltin Aryl Selenides as Efficient Arylselenating Agents. Synthesis of Diaryl and Aryl Organyl Selenides

Abstract: Tributyltin aryl selenides are highly efficient arylselenating agents in reactions with aryl iodides and aryl triflates under catalysis with Pd and Ni complexes respectively. They also may be used as efficient source of active arylselenolate anion in the presence of fluoride ions in reaction of arylselenation of alkyl halides and activated aryl fluorides.

Reactions of Methyl 4-Aminofurazan-3-carboximidate with Nitrogen-Containing Nucleophiles

Abstract: Methyl 4-aminofurazan-3-carboximidate reacts with aromatic amines and hydrazines to give the corresponding amidines and amidrazones. The reaction of the title compound with o-phenylenediamine yields 3-amino-4-(2-benzimidazolyl)furazan, and with acylhydrazines N2-acyl-4-aminofurazan-3-carbohydrazides are formed. The latter undergo thermal intramolecular cyclization with formation of 3-amino-4-(1,2,4-triazol-3-yl)furazan derivatives containing various substituents in position 5 of the triazole ring.

Ionic Hydrogenation of α,β-Unsaturated Ketones with Cyclohexane in the Presence of Aluminum Halides

Abstract: 4-Methyl-3-penten-2-one, 3-hepten-2-one, 3-methyl-1-phenyl-2-buten-1-one, 4-(2,4-dichlorophenyl)-, 4-(4-hydroxyphenyl)-, 4-(4-methoxyphenyl)-, 4-(2-hydroxyphenyl)-, and 4-(4-dimethylaminophenyl)-3-buten-2-ones, and 3-(4-methoxyphenyl)-1-phenyl-2-propenone react with cyclohexane in the presence of excess aluminum chloride or aluminum bromide in CH2Cl2 or CH2Br2, respectively, at room temperature to form the corresponding saturated ketones in high yields. Using 4-phenyl- and 4-(4-methoxyphenyl)-3-buten-2-ones as examples, it was shown that the reaction pattern does not change in going from the Lewis acids AlCl3 and AlBr3 to proton-donor acid system CF3SO3H-SbF5. The reactive intermediates are likely to be C-protonated complexes of α,β-unsaturated ketones with aluminum halides or their O,C-diprotonated analogs.

Synthesis, X-Ray Diffraction Data, and 1H and 13C NMR Spectra of N-(N-Arylsulfonylimidoyl)-1,4-benzoquinonimines Derived from N-Aroyl(acetyl)-1,4-benzoquinonimines

Abstract: Oxidation of N-(N-arylsulfonylimidoyl)-4-aminophenols gave the corresponding N-[N-arylsulfonylimidoyl)-1,4-benzoquinonimines, derivatives of N-aroyl- and N-acetyl-1,4-benzoquinonimines. The structure of the products was studied by the X-ray diffraction method and 1H and 13C NMR spectroscopy. N-(N-Arylsulfonylimidoyl)-1,4-benzoquinonimines were found to undergo fast (on the NMR time scale) Z E isomerization about the CIN bond in the quinonimine fragment. N-(N-Arylsulfonylacetimidoyl)-1,4-benzoquinonimines in solution give rise to dynamic Z E-isomerization with respect to the CIN bond in the N-arylsulfonylacetimidoyl fragment.

Quantum-Chemical Treatment of Cyclization Reactions: XXIV. Superposition-Additivity Approach

Abstract: The superposition-additivity approach which is characterized by a very simple calculation scheme provides a sufficiently reliable description of electronic structure, physicochemical parameters, and chemical behavior (specifically, in electrocyclic ring closure reactions) of large organic molecules with conjugated double bonds on the basis of the calculation or experimental data for less extended analogs.

Porphyrins and Their Derivatives: XXII. A New Product of Intramolecular Cyclization of 5,10,15,20-Tetraphenyl-2-formylporphyrin Copper Complex

Abstract: The treatment at boiling of 5,10,15,20-tetraphenyl-2-formylporphyrin copper(II) with saturatedsolution of p-chloranil in benzene in the presence of 70% aqueous trifluoroacetic acid affords alongsideverdin (16.7%) its isomer with a keto group located in the β-position of the macrocycle in 71% yield.

Kinetics and Mechanism of Izomerization of N-Alkoxycarbonyl-5-aroxytetrazoles *

Abstract: The kinetics and mechanism of the N2-N1-isomerization of 2-methoxycarbonyl-5-(p-X-phenoxy)- tetrazoles (X = H, CH3, NHCOCH3, Cl, Br, NO2) were studied by 1H NMR spectroscopy in a DMSO-d6-CDCl3 mixture (25:75). The rate of isomerization of the N2-isomer into N1-isomer fit the first-order equation (after three half-conversion periods). The isomerization is accompanied by hydrolysis and decarboxylation. The Hammett plot of ln(kXkH) for the isomerization showed a good correlation with σ- values (ρ- = 1.33, r = 0.965). A poor correlation with σ values was obtained. The kinetic data, the effect of solvent polarity, the substituent effects, and the results of AM1 quantum-chemical calculations suggest an ionic mechanism of the isomerization in polar solvents and a concerted mechanism in nonpolar solvents.

Synthesis of Thymidine Derivatives as Potential Pharmaceuticals against HIV/AIDS Infection

Abstract: Data on preparation methods for 3'-modified oxythymidines are summarized and systematized. A synthesis tree is presented permitting a selection of rational schemes for thymidine derivatives preparation, in particular those that can be potential anti-HIV/AIDS drugs.

Adamantylazoles: IV* acid-catalyzed adamantylation of pyrazoles

Abstract: Pyrazoles with pKBH+ no more than 0.8 and having substituents in 3(5) position with effective van der Waals radii not exceeding 2 A in a mixture of phosphoric and acetic acids at weight ratio 4:1 (H0 -1,8) react with 1-adamantanol to afford the corresponding 1-(1-adamantyl)- or 1,4-di(1-adamantyl)pyrazoles.

4-Functionally Substituted 3-Heterylpyrazoles: IV. 1-Phenyl-3-aryl(heteryl)-5-(4-pyrazolyl)-2-pyrazolines

Abstract: 3-Aryl(heteryl)-4-formylpyrazoles in condensation with methyl aryl(heteryl) ketones afforded 1-aryl(heteryl)-3-[3-aryl(heteryl)-4-pyrazolyl]propenones. The latter reacted with phenylhydrazine yielding 1-phenyl-3-aryl(heteryl)-5-(4-pyrazolyl)-2-pyrazolines.

5-Substituted 3-Nitro-1-vinyl-1,2,4-triazoles

Abstract: A series of 5-substituted 3-nitro-1-vinyl-1,2,4-triazoles were synthesized by alkaline treatment of the corresponding 1-(2-haloethyl- or 2-nitroxyethyl)-3-nitro-1,2,4-triazoles and by transvinylation of NH acids of the same series with vinyl acetate. The scope of applicability of the transvinylation procedure was established with respect to the azole pKa value. The vinylic double bond on the nitrogen was shown to be inactive toward both nucleophilic and electrophilic reagents, whereas the halogen atom in position 5 exhibits enhanced reactivity. The latter factor provides the possibility for versatile structural modification via nucleophilic replacement of the 5-halogen atom by various groups, including triazolate ion.

Thermolysis of 6-Aryl-1,5-diazabicyclo[3.1.0]hexanes in the Presence of N-Arylmaleimides

Abstract: Heating of 6-aryl-1,5-diazabicyclo[3.1.0]hexanes in the presence of N-arylmaleimides gives rise to 2,9-diarylperhydropyrazolo[1,2-a]pyrrolo[3,4-c]pyrazole-1,3-diones. It is presumed that thermal cleavage of the C-N bond in the diaziridine fragment of the 6-aryl-1,5-diazabicyclo[3.1.0]hexanes results in formation of labile azomethinimines that react with N-arylmaleimides to afford the products of 1,3-dipolar cycloaddition. The rate of accumulation thereof depends only on the character of substituents in the aromatic ring of the 1,5-diazabicyclo[3.1.0]hexanes and is independent of maleimide. The thermal isomerization of 6-aryl-1,5-diazabicyclo[3.1.0]hexanes without 1,3-dipolarophiles yields the corresponding 2-pyrazolines.

Adamantylation of Imidazoles and Benzimidazole

Abstract: For the first time is reported on substitution of a hydrogen atom in position 4 of the imidazole ring with an aliphatic substituent occurring in reaction between 1-bromoadamantane and imidazoles. The reaction proceeds alongside the substitution in position 1 at heating in excess imidazole. In o-dichlorobenzene solution adamantylation of benzimidazole afforded 1-(1-adamantyl)benzimidazole and 1,3-di(1-adamantyl)benzimidazolium bromide. The specific features of the reactions course are described. The structure of compounds obtained is proved by 1H NMR spectroscopy.

Reactions of N- and C-Alkenylanilines: II. Halocyclization of 2-(2-Cycloalkenyl)anilines

Abstract: The reaction of 2-(2-cyclopentenyl)anilines with I2 in the presence of NaHCO3 results in formation of 3-iodocyclopenta[b]indoles in high yields. Under similar conditions 2-(2-cyclohexenyl)anilines give rise to cyclization products whose structure depends on the solvent and substituents in the aromatic ring and on the nitrogen atom.