Tetrazoles: LV. Perparation of 2-anilino-5-aryl(hetaryl)-1,3,4-oxadiazoles from 5-substituted tetrazoles under microwave activation

In reaction of 5-aryl(hetaryl)tetrazoles with phenyl isocyanate under the conditions of microwave activation the corresponding 2-anilino-5-aryl(hetaryl)-1,3,4-oxadiazoles formed in high yields. The application of the microwave activation fourfold reduced the reaction time.     

Efficient Photooxidation of Aryl(hetaryl)pyrazolines by Benzoquinone

Photooxidation of aryl(hetaryl)pyrazolines in the presence of benzoquinone has been studied in organic solvents. This reaction occurs at high rate to provide the corresponding pyrazole in a good yield. The effects of the solvent, pyrazoline structure and oxygen provide definite information on the reaction pathway. It appears that radical species are intermediates in the photooxidation of aryl(hetaryl)pyrazolines in the presence of benzoquinone. A comparison of the new results with the photooxidation of aryl(hetaryl)pyrazolines in the presence of perchloroalkanes is also discussed.     

Plant coumarins: XI. Cross coupling reactions with 2-(tosyl)oreoselone

The reaction of a linearly fused furocoumarin, oreoselone, with p-toluenesulfonyl chloride gave 2-tosyloreoselone which showed a high reactivity in palladium-catalyzed cross-coupling reactions with formation of a new carbon-carbon bond. 2-Tosyloreoselone reacted with terminal alkynes in the presence of Pd(PPh₃)₂Cl₂ to give the corresponding 2-alkynylfuro[3,2-g]chromen-3-ones. 2-Aryl(hetaryl)alkynyloreoselones were obtained in high yield directly by palladium-catalyzed reaction of oreoselone with tosyl chloride and aryl(hetaryl)acetylenes. The reaction of 2-tosyloreoselone with aryl(hetaryl)boronic acids in the presence of palladium complexes with uni- and bidentate ligands, tetrabutylammonium bromide, and a base afforded 2-aryl(hetaryl)-substituted oreoselones. 2-Vinyloreoselone was synthesized from 2-tosyloreoselone and potassium trifluoro(vinyl)borate.     

One-pot assembly of 4-methylene-3-oxa-1-azabicyclo[3.1.0]hexanes from alkyl aryl(hetaryl) ketoximes, acetylene, and aliphatic ketones: a new three-component reaction

A new three-component reaction between alkyl aryl(hetaryl)ketoximes, acetylene, and aliphatic ketones in the superbasic systems KOH/DMSO and LiOH/CsF/DMSO (70-90 °C, initial acetylene pressure 13-15 atm, 5-60 min) affords novel 4-methylene-3-oxa-1-azabicyclo[3.1.0]hexanes in yields of up to 75%. Using KOH/DMSO, the side products of the reaction are O-vinylketoximes and 2-aryl(hetaryl)pyrroles, while with LiOH/CsF/DMSO, the reaction proves to be selective, only minor amounts of the corresponding alkyl aryl(hetaryl) ketones being detectable.     

Study of plant coumarins: X. Peurutenicin triflate in cross-coupling reactions

By Suzuki cross-coupling reaction of peurutenicin triflate with arylboric, furanylboric, pyridinylboric, and indolylboric acids the corresponding 7-aryl(hetaryl)coumarins were synthesized. The high activity of hetaryl-substituted boric acids in the Suzuki reaction was observed. Heck reaction of 7-O-trifluoromethylsulfonylpeur utenicin with terminal olefins (styrene, vinylpyridines, vinylpyrazine, vinyltriazole) was used to prepare (E)-7-[aryl(hetaryl)vinyl]coumarins. The dependence of reaction products yield on the nature of the catalytic system was found.     

Synthesis of 2-aryl(hetaryl)-1-hydroxyimidazoles by the reaction of aliphatic 1,2-hydroxylamino oximes with aromatic and heteroaromatic aldehydes

A reaction of aliphatic 1,2-hydroxylamino oximes bearing the hydroxylamino group at the secondary carbon atom with aromatic and heteroaromatic aldehydes in acetic acid leads to the corresponding 1-hydroxy-2-aryl(hetaryl)-4,5-dialkylimidazoles in high yields. α-Aryl(hetaryl)-nitrones initially formed by the condensation of 1,2-hydroxylamino oximes with aldehydes are quantitatively converted to the corresponding imidazoles.     

Synthesis of 7-acetyl-8-aryl(hetaryl)- 6-hydroxy-1,6-dimethyl-3-selenoxo-2,3,5,6,7,8-hexahydroiso-quinoline-4-carbonitriles by the condensation of 2,4-diacetyl-3-aryl(hetaryl)- 5-hydroxy-5-methyl-cyclohexanones with cyanoselenoacetamide

7-Acetyl-8-aryl(hetaryl)-6-hydroxy-1,6-dimethyl-3-selenoxo-2,3,5,6,7,8-hexahydroisoquinoline-4-carbo- nitriles have been obtained by the condensation of 2,4-diacetyl-3-aryl(hetaryl)-5-hydroxy-5-methyl-cyclohexanones with cyanoselenoacetamide.     

First acetylenic derivatives of stable 3-imidazoline nitroxides

The Stephens-Castro reaction of copper(I) salts of 1-aryl(hetaryl)alkynes with 2,2,5,5-tetramethyl-4-[2-(4-iodophenyl)-vinyl]imidazoline-3-oxide-1-ol proved to be a general method for the preparation of 2,2,5,5-tetramethyl-4-[2-(p-aryl(hetaryl)ethynylphenyl)]vinyl-3-imidazoline-3-oxide-1-oxyles.     

Addition of Nitrile Oxides to Allyl Esters of Aryl(hetaryl)carboxylic Acids

3,5-Disubstituted isoxazolines with an aryl(hetaryl)carboxymethyl group in position 5 have been synthesized. The addition reaction of nitrile oxides to allyl esters of aryl(hetaryl) carboxylic acids occurs regiospecifically with the formation of the 5-substituted isomer. Initial pharmacological screening showed that 5-(4-bromobenzoyloxy)methyl-3-(3,4-dimethoxyphenyl)isoxazoline possesses marked nootropic activity.     

Interaction of N,N-dimethylhydrazonomethyl and α-hydroxyketone groups in hetaryl analogs of unsymmetrical benzoins

The reaction of phenylglyoxal hydrate with N,N-dimethylhydrazones of furfural and 1-methylpyrrole-2-carbaldehyde proceeds regioselectively at position 5 of the heterocycle. The hetaryl analogs of α-benzoins obtained are quantitatively isomerized into the isomeric β-benzoins. The N,N-dimethylhydrazonomethyl group, while activating the hetaryl residue, reduces the time for isomerization compared with unfunctionalized benzoins. The N, N-dimethylhydrazonomethyl group is readily transformed into an aldehyde or nitrile group and enters into a trans-hydrazonation reaction. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, pp. 1805–1814, December, 2005.     

Efficient synthesis of 3-aryl(hetaryl)-1,5,3-dioxazepanes involving catalysts containing Sm and Co

Efficient synthetic procedure was developed for 3-aryl(hetaryl)-1,5,3-dioxazepanes consisting in the transamination of 3-tert-butyl-1,5,3-dioxazepane with arylamines and also by the reaction of 1,2-ethanediol with N,N-bis(methoxymethyl)aryl(hetaryl)amines in the presence of catalytic amounts of Sm and Co compounds.     

Stable nitroxyl radicals with triple bonds: 4-acetylenyl-3-imidazoline-3-oxide-1-oxyls

Cross-coupling reaction of 1-hydroxy-2,2,5,5-tetramethyl-4-[2-(p-iodophenyl)vinyl]-3-imidazoline-3-oxide with copper(I) salts of 1-aryl(hetaryl)alkynes leads to the corresponding 2,2,5,5-tetramethyl-4-[2-(p-aryl(hetaryl)ethynylphenyl)vinyl]-3-imidazoline-3-oxide-1-oxyls in high yields.     

A convenient synthesis of 3,4-diaryl(hetaryl)-substituted maleimides and maleic anhydrides

A convenient procedure has been developed for the synthesis of 3,4-diaryl(or hetaryl)maleimides by cross coupling of N-substituted 3,4-dibromomaleimides with aryl(hetaryl)boronic acids in the presence of Pd(Ph₃P)₄ and CsF. The reaction ensures high yields of the products and requires relatively small amount of the catalyst; it can be performed on an enlarged scale. The resulting maleimides are readily converted into the corresponding maleic anhydrides.     

Chemosensor activity of 2-(anthracen-9-yl)-substituted imidazolidines and hexahydropyrimidines

A number of 2-(anthracen-9-yl)-substituted imidazolidines and hexahydropyrimidines were synthesized by reaction of N,N′-bis[aryl(hetaryl)methyl]ethylene-1,2-diamines and N,N′-bis[aryl(hetaryl)methyl]-propane-1,3-diamines with anthracene-9-carbaldehyde. The obtained compounds showed chemosensor activity toward Cd²⁺, Cu²⁺, and Hg²⁺ ions.     

Reaction of aroyl- and hetaroyltrifluoroacetones with acylhydrazines: Regioselectivity and tautomerism of the condensation products

Acylhydrazines react with 1,3-diketones of the general formula CF₃COCH₂COR (where R is an aryl or hetaryl group) at both carbonyl groups. The reaction at the trifluoroacetyl group is favored by donor substituents in the aromatic ring of the 1,3-diketone or by the 2-furyl and, especially, 2-thienyl group as a hetaryl substituent, as well as by elevated temperature. The condensation products at the carbonyl group contiguous to the aryl or hetaryl ring have the structure of 5-hydroxy-4,5-dihydropyrazoles and do not undergo tautomeric transformations in solution. The condensation products at the trifluoroacetyl group have either 5-hydroxy-4,5-dihydropyrazole or hydrazone structure and give rise to ring-chain tautomeric equilibrium in solution. Electron-withdrawing substituents in the aromatic ring of the 1,3-dicarbonyl fragment and CDCl₃ as solvent favor formation of the cyclic tautomer. The state of the tautomeric equilibrium is weakly sensitive to structural variations in the hydrazine component.     

Reactions of alkyl hetaryl ketones with carbon tetrachloride under liquid/solid phase-transfer catalysis conditions

Summary Reactions of methyl and ethyl hetaryl ketones in the CCl₄/solid KOH system in the presence of 18 crown-6 at room temperature yield the corresponding 2-hetaryl-2-trichloromethyloxiranes in 8–22% yields. Reactions of sterically hindered ketones of the type (hetaryl)COCHR₂ (R = Me, Et) with CCl₄/OH- form the corresponding a-hydroxy ketones of the type (hetaryl)COC(OH)R₂ in 28–44% yields.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 312–315, March, 1994.     

Regioselectivity in the reaction of paraformaldehyde with (1S,2S)-2-aryl(hetaryl)methylamino-1-(4-nitrophenyl)-1,3-propanediols

The reaction of paraformaldehyde with (1S,2S)-2-aryl(hetaryl)methylamino-1-(4-nitrophenyl)-1,3-propanediols produces a mixture of isomeric 3-aryl(hetaryl)methyl-4-hydroxymethyl-5-(4-nitrophenyl)- and 3-aryl(hetary)methyl-4-hydroxy(4-nitrophenyl)methyloxazolidines and is reversible. Université d'Auvergne, Faculté de Farmacie, 28, Place Henri Dunant, Clermont-Ferrand, France. Samara State University, Samara 443011, Russia. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 536–541, April, 1999.     

Tetrazoles: LIII. Microwave-activated acylation of 5-substituted tetrazoles

The acylation of 5-aryl(hetaryl)tetrazoles with acetic and benzoic anhydrides under microwave irradiation gave the corresponding 2-substituted 5-methyl-and 5-phenyl-1,3,4-oxadiazoles in high yields. The use of microwave activation reduces the reaction temperature by 30–40°C and shortens the reaction time by a factor of 5 to 7.     

One-pot,three-component cascade synthesis of new tetrasubstituted pyrroles by coupling reaction of 2-functionally substituted 2-alkenals,amines, and nitroethane

The reactivity of 2-alkylthio(2-alkoxy)-substituted 3-aryl(hetaryl)propenals in a one-pot, three-component reaction with primary amines and nitroethane has been studied. A method for the synthesis of highly functionalized pyrroles (in 36–80% yield) from 2-alkylthiopropenals has been developed on the basis of this reaction. It is found that the reaction proceeds via formation of the intermediate imine of the starting enal, which undergoes 1,2-addition by nitroethane to give kinetically controlled 2-alkylthio-3-alkylamino-1-aryl(hetaryl)-4-nitropentene. When left to stand, upon heating or under microwave assistance, this adduct can be transformed into the thermodynamically controlled 1,4-adduct. The latter undergoes intramolecular cyclization to afford the target pyrrole. A possibility of such isomerization of addition products of nitroalkane to 2-functionalized α,β-unsaturated imines is revealed for the first time. Scope of the reaction depending upon its conditions as well as structure of the starting substrates and amines has been studied.     

A Noncatalytic Approach to Hetaryl‐Annulated 1,2,4‐Thiadiazine‐1,1‐dioxides

A set of synthetic procedures was developed to yield functionalized pyrido‐, pyrimido‐, and thiazo‐annulated thiadiazine‐1,1‐dioxides on a preparative scale. In all cases the thiadiazine‐1,1‐dioxide ring closure was carried out through a reaction of hetaryl‐sulfonyl chlorides with amidines under mild noncatalytic conditions. In the case of 2‐chloropyridine‐3‐sulfonyl chloride derivatives and 2,4‐dichlorothiazole‐5‐sulfonyl chloride open‐chain sulfonylated amidine intermediates were isolated and then subjected to the cyclization step. The reaction with 2,4‐dichloropyrimidine‐5‐sulfonyl chloride gave rise to the corresponding thiadiazine‐1,1‐dioxides in one‐pot. Similarly, a reaction of 2‐chloropyridine‐3‐sulfonamide with lactime ethers proceeded in one‐pot readily giving the corresponding thiadiazine‐1,1‐dioxides. Remaining chlorine atoms on the prepared hetaryl‐annulated benzothiadiazine‐1,1‐dioxides readily undergo aromatic nucleophilic displacement reactions serving thus as additional variation points for the design of biologically potent compounds.