Cyclocondensation of <Emphasis Type="Italic">N</Emphasis>-aryl-3-oxobutanethioamides with 1<Emphasis Type="Italic">H</Emphasis>-1,2,4-triazol-5-amine

Reactions of N-aryl-3-oxobutanethioamides with 1H-1,2,4-triazole-5-amine give mixtures of 7-arylamino-5-methyl[1,2,4]triazolo[1,5-a]pyrimidines, 5-methyl-4,7-dihydro[1,2,4]triazolo[1,5-a]pyrimidine-7-thione, 7-methyl-4,5-dihydro[1,2,4]triazolo[1,5-a]pyrimidine-5-thione, and 5-arylamino-7-methyl[1,2,4]triazolo[ 1,5-a]pyrimidines whose ratio depends on the substituent in the aryl group of initial N-aryl-3-oxobutanethioamide and solvent nature (the presence of a proton-donor solvent).     

Synthesis of methyl 7-aryl-6-(2-thenoyl)-4,7-dihydro-tetrazolo[1,5-<Emphasis Type="Italic">a</Emphasis>]pyrimidine-5-carboxylates and their reaction with hydrazine hydrate

Fusion of methyl 4-(2-thienyl)-2,4-dioxobutanoate with 1H-tetrazol-5-amine monohydrate and aromatic aldehyde gave methyl 7-aryl-6-(2-thenoyl)-4,7-dihydrotetrazolo[1,5-a]pyrimidine-5-carboxylates which reacted with an equimolar amount of hydrazine hydrate at 180–190°C under solvent-free conditions to produce 9-aryl-8-(2-thienyl)-4,9-dihydrotetrazolo[1′,5′: 1,2]pyrimido[4,5-d]pyridazin-5(6H)-ones.     

Synthesis of diethyl 6-aryl-3,6-dihydrotetrazolo-[1,5-<Emphasis Type="Italic">a</Emphasis>]pyrimidine-4,5-dicarboxylates

Three-component condensation of diethyl 2-oxobutanedioate sodium salt with aromatic aldehydes and tetrazol-5-amine monohydrate afforded the corresponding diethyl 6-aryl-3,6-dihydrotetrazolo[1,5-a]pyrimidine-4,5-dicarboxylates.     

Synthesis of alkyl 7-aryl-6-aroyl-4,7-dihydrotetrazolo[1,5-<Emphasis Type="Italic">a</Emphasis>]pyrimidine-5-carboxylates

Reactions of alkyl aroylpyruvates with a mixture of aromatic aldehyde and 5-aminotetrazole led to the formation of alkyl 7-aryl-6-aroyl-4,7-dihydrotetrazolo [1,5-а] pyrimidine-5-carboxylates.     

A novel magnetically recyclable silver-loaded cellulose-based bionanocomposite catalyst for green synthesis of tetrazolo[1,5-<Emphasis Type="Italic">a</Emphasis>]pyrimidines

5-Methyl-7-aryl-4,7-dihydrotetrazolo[1,5-a]pyrimidine-6-carboxylic ester derivatives were efficiently synthesized by reaction of methyl or ethyl acetoacetate, 5-aminotetrazole (produced from 2-cyanoguanidine and sodium azide), and various aromatic aldehydes in presence of a new cellulose-based Ag-loaded magnetic bionanostructure. This protocol offers many advantages such as short reaction time, high yield, the remarkable magnetic property of the nanocomposite, and easy separation of the nanocatalyst from the reaction mixture without considerable loss of catalytic activity. Furthermore, X-ray diffraction analysis, field-emission scanning electron microscopy, and energy-dispersive X-ray (EDX) analysis were used to characterize the prepared nanocatalyst.     

2-amino-4,5,6,7-tetrahydro-1,2,4-triazolo[1,5-<Emphasis Type="Italic">a</Emphasis>]pyrimidines: Synthesis and reactions with electrophilic reagents

The hydrogenation of 2-amino-5-R-7-R′-4,7-dihydro-1,2,4-triazolo[1,5-a]pyrimidines with NaBH₄ led to the formation of 2-amino-5-R-7-R′-4,5,6,7-tetrahydro-1,2,4-triazolo[1,5-a]pyrimidines. Acylation, sulfonylation, and alkylation of these compounds depending on conditions and the reagent character occur at the amino group, atoms N³ or N⁴. The treatment with alkali of 2-amino-3-benzyl-5-R-7-R′-4,5,6,7-tetrahydro-1,2,4-triazolo-[1,5-a]pyrimidinium bromide resulted in 2-amino-3-benzyl-5-R-7-R′-3,5,6,7-tetrahydro-1,2,4-triazolo[1,5-a]-pyrimidine, similar reaction of 2-acetamido-3-benzyl-5-R-7-R′-4,5,6,7-tetrahydro-1,2,4-triazolo[1,5-a]-pyrimidinium bromide gave a mesoionic product of a hydrogen elimination from the amide nitrogen atom.     

A new approach to synthesis of 2-sulfonylamino-1,2,4-triazolo[1,5-<Emphasis Type="Italic">a</Emphasis>]pyrimidines

A procedure for synthesis of 2-sulfonylamino-1,2,4-triazolo[1,5-a]pyrimidines by sulfonylation of 2-amino-4,7-dihydro-1,2,4-triazolo[1,5-a]pyrimidines, followed by oxidation of intermediate 2-sulfonylamino-4,7-dihydro-1,2,4-triazolo[1,5-a]pyrimidines, was suggested.     

Cyclocondensation of <Emphasis Type="Italic">N</Emphasis>-aryl-3-oxobutanethioamides with 2-aminoimidazole and 2-aminobenzimidazole

Cyclization of N-aryl-3-oxobutanethioamides with 2-aminoimidazole and 2-aminobenzimidazole gave 7-methyl-5,8-dihydroimidazo[1,2-a]pyrimidine-5-thione or 2-methylpyrimido[1,2-a]benzimidazole-4(1H)-thione and 4-(arylamino)-2-methylpyrimido[1,2-a]benzimidazoles whose ratio depends on the nature of aryl substituents in the initial butanethioamides and on the presence of a protic solvent.     

Synthesis of derivatives of pyrazolo[1,5-<Emphasis Type="Italic">a</Emphasis>]pyrimidines and imidazo[1,5-<Emphasis Type="Italic">a</Emphasis>]pyrimidines proceeding from alkyl 2-benzylidene-3-oxo-3-fluoroalkylpropionates

Methods were developed of the synthesis of alkyl 2-hydroxy-2-fluoroalkyl-4-phenyl-1,2,3,4—tetrahydroimidazo-[1,5-a]pyrimidine-3-carboxylates and alkyl-5-hydroxy-2,7-diphenyl-5-fluoroalkyl-4,5,6,7-tetrahydropyrazolo[1,5-a]pyrimidine-6-carboxylates by regioselective [3+3]-cycloaddition of 5-aminoimidazole or 5-aminopyrazole to alkyl 2-benzylidene-3-oxo-3-fluoroalkylpropionates at the fluoroacylvinyl fragment.     

Reaction of <Emphasis Type="Italic">N</Emphasis>-aryl-3-oxobutanethioamides with 2-amino-1,3-thiazole and 2-amino-1,3-benzothiazole

N-Aryl-3-oxobutanethioamides react with 2-amino-1,3-thiazole (2-amino-1,3-benzothiazole) in acetic acid to give mixtures of 7-methyl-5H-[1,3]thiazolo[3,2-a]pyrimidine-5-thione (2-methyl-4H-pyrimido-[2,1-b][1,3]benzothiazole-4-thione) and 5-arylimino-7-methyl-5H-[1,3]thiazolo[3,2-a]pyrimidines (4-arylimino-2-methyl-4H-pyrimido[2,1-b][1,3]benzothiazoles), whose ratio depends on the nature of the aryl substituent in the initial butanethioamide.     

Synthesis of New Cyclopenta[<Emphasis Type="Italic">b</Emphasis>]quinoline Derivatives

A series of new 11-(R-phenyl)-8,9-dihydro-7H-benzo[f]cyclopenta[b]quinolin-10(11H)-ones and 7,14-bis(R-phenyl)-2,3,9,10,11,14-hexahydrocyclopenta[2,3]quinolino[8,7-h]cyclopenta[b]quinoline-1,8(4H,7H)-diones were synthesized by three-component condensation of naphthalen-2-amine or naphthalene- 1,5-diamine with substituted benzaldehydes and cyclopentane-1,3-dione in one step through intermediate formation of unstable arylaminoketoenol.     

Synthesis and hypoglycemic activity of methyl-6-aryl(hetaryl)-5-(2-furanoyl)-3,6-dihydrotetrazolo[1,5-<Emphasis Type="Italic">a</Emphasis>]pyrimidine-4-carboxylates

Three-component reaction of methyl 2-furanoylpyruvate with an aromatic aldehyde and 5-aminotetrazole monohydrate has afforded methyl 6-aryl(hetaryl)-5-(2-furanoyl)-3,6-dihydrotetrazolo[1,5-a]-pyrimidine-4-carboxylates. Hypoglycemic activity of the prepared compounds has been studied.     

Synthesis and study of the azide-tetrazole tautomerism in 2-azido-4-(trifluoromethyl)-6-R-pyrimidines (R = H, 4-ClC<Subscript>6</Subscript>H<Subscript>4</Subscript>)

Azide-tetrazole equilibrium in azidopyrimidines bearing trifluoromethyl group on the example of 2-azidopyrimidines has been studied. The latter were synthesized via nitrosation of 2-hydrazino-4-trifluoromethylpyrimidine and reaction of NaN₃ with 4-trifluoromethyl-2- chloro-6-(4-chlorophenyl)pyrimidine. The tautomeric equilibrium 5-trifluoro methyl tetrazolo[1,5-a]pyrimidine ? 2-azido-4-trifluoromethylpyrimidine was observed in the absence of solvent and in DMSO-d₆ solution, whereas in CDCl³ only an azide form exists. For 2-azido- 4-trifluoromethyl-6-(4-chlorophenyl)pyrimidine, only an azide isomer was detected in CDCl³ solution, and in DMSO-d₆ solution it is in equilibrium with 5-(trifluoromethyl)-7-(4-chlorophenyl) tetrazolo[1,5-a]pyrimidine (the tautomer ratio is 99 : 1). Thermodynamic and kinetic parameters of 5-trifluoromethyltetrazolo[1,5-a]pyrimidine ? 2-azido-4-trifluoromethylpyri midine tautomeric rearrangement in DMSO-d₆ for 5-trifluoromethyltetrazolo[1,5-a]pyrimidine were determined using the exchange spectroscopy (EXSY) technique.     

Condensation of fluorine-substituted benzaldehydes with amines and cyclic ketones

Condensation of fluorine-containing benzaldehydes with naphthalen-2-amine or quinolin-6-amine and cyclic ketones (cyclopentanone, cyclohexanone, and 4-methylcyclohexanone) gave new fluorine-containing derivatives of cyclopenta[c]benzo[f]quinoline, benzo[a]phenanthridine, and cyclopenta[a]- and benzo[a]-[4,7]phenanthroline. Intermediate products, 2-[(fluorophenyl)(2-naphthylamino or quinolin-6-ylamino)methylidene] cyclohexanones, dihydrobenzo[f]quinolines, and dihydro-4,7-phenanthrolines, were isolated.     

Thermal Rearrangements of 3<Emphasis Type="Italic">H</Emphasis>- and 4<Emphasis Type="Italic">H</Emphasis>-Pyrazoles Prepared by Reactions of 9-Diazofluoren with Methyl Tetrolate and Methyl 3-Phenylpropiolate

9-Diazofluoren adds in Et₂O at 20°C to methyltetrolate in keeping with Auwers rule and nonregioselectively adds to methyl-3-phenylpropiolate with the formation of spirocyclic 3H-pyrazoles. The methyltetrolate adduct at boiling in toluene converts into methyl 3a-methyl-3aH-dibenzo[e,g]indazole-3-carboxylate, at 190°C in benzene, into methyl 3-methyl-2H-dibenzo[e,g]indazole-2-carboxylate, and at 160°C in methanol, into 3-methyl-2H-dibenzo[e,g]indazole. Auwers adduct of methyl 3-phenylpropiolate at boiling in benzene gives cyclopropene derivative and at boiling in methanol isomerizes into methyl 3a-phenyl-3aHdibenzo[e,g]indazole-3-carboxylate. Anti-Auwers adduct at boiling in benzene isomerizes into methyl 2-phenylpyrazolo[1,5-f]phenanthridine-3-carboxylate.     

Five-membered 2,3-dioxo heterocycles: LXXX. Recyclization of 1H-pyrrole-2,3-diones into pyrazolo[1,5-a]pyrimidines by the action of pyrazolamine. Crystalline and molecular structure of substituted pyrazolo[1,5-a]pyrimidine

Methyl 1-aryl-3-aroyl-4,5-dioxo-4,5-dihydro-1H-pyrrole-2-carboxylates reacted with 3-methyl-4-phenyl-1H-pyrazol-5-amine to give methyl 7-arylcarbamoyl-6-aroyl-2-methyl-3-phenylpyrazolo[1,5-a]-pyrimidine-5-carboxylates. The molecular and crystalline structures of methyl 6-benzoyl-7-(4-chlorophenylcarbamoyl)-2-methyl-3-phenylpyrazolo[1,5-a]pyrimidine-5-carboxylate were studied by X-ray analysis.     

Electrophilic heterocyclization of 6-alken(yn)ylsulfanyl-pyrazolo[3,4-<Emphasis Type="Italic">d</Emphasis>]pyrimidin-4(5<Emphasis Type="Italic">H</Emphasis>)-ones

6-Allylsulfanyl-1-arylpyrazolo[3,4-d]pyrimidin-4(5H)-ones react with iodine and sulfuric acid to give angular pyrazolothiazolopyrimidine derivatives. The reaction of 6-(prop-2-yn-1-ylsulfanyl)-1-(4-tolyl)-pyrazolo[3,4-d]pyrimidin-4(5H)-one with sulfuric acid gives angularly fused pyrazolo[4,3-e][1,3]thiazolo-[3,2-a]pyrimidin-4-one, whereas in the reaction with sodium methoxide linearly fused pyrazolo[3,4-d][1,3]-thiazolo[3,2-a]pyrimidin-4-one was formed. Linearly fused pyrazolo[3′,4′:4,5]pyrimido[2,1-b][1,3]thiazole derivatives were also obtained by reaction of 1-aryl-6-(3-phenylprop-2-en-1-ylsulfanyl)pyrazolo[3,4-d]pyrimidin-4(5H)-ones with sulfuric acid.     

Synthesis of Pyrano[4′,3′:2,3]pyrrolo[1,2-<Emphasis Type="Italic">a</Emphasis>]quinoxalines by Reaction of Aroylpyrroloquinoxalines with Alkyl Vinyl Ethers

Thermally induced [4 + 2]-cycloaddition of 3-aroylpyrrolo[1,2-a]quinoxaline-1,2,4(5H)-triones with alkyl vinyl ethers afforded mixtures of diastereoisomeric (5S*,6aR*)- and (5R*,6aR*)-5-alkoxy-3-aryl-5,6-dihydropyrano[ 4′,3′: 2,3]pyrrolo[1,2-a]quinoxaline-1,2,7(8H)-triones.     

Synthesis of N-substituted 7-aryl-5-methyl-4,7-dihydrotetrazolo[1,5-<Emphasis Type="Italic">a</Emphasis>]pyrimidine-6-carboxamides

Three-component reaction of N-methyl- or N,N-diethyl-3-oxobutanamide with aromatic aldehydes and tetrazol-5-amine monohydrate gave the corresponding N-substituted 7-aryl-5-methyl-4,7-dihydrotetrazolo-[1,5-a]pyrimidine-6-carboxamides.     

Synthesis and Structure of 4-Indolyl-5-(thieno[3,2-<Emphasis Type="Italic">b</Emphasis>]pyrrol-6-yl)imidazoles

A procedure was proposed for regioselective acylation of methyl 2-methyl-4H-thieno[3,2-b]-pyrrole-5-carboxylate with 2-(3-indolyl)-2-oxoacetyl chloride. Reactions of the resulting methyl 6-[2-(3-indolyl)-1,2-dioxoethyl]-2-methyl-4H-thieno[3,2-b]pyrrole-5-carboxylate with aromatic aldehydes and ammonium acetate in acetic acid afforded the corresponding methyl 6-[2-aryl-4-(3-indolyl)imidazol-5-yl]-2-methyl-4H-thieno[3,2-b]pyrrole-5-carboxylates. The structure of methyl 6-[2-(4-chlorophenyl)-4-(3-indolyl)imidazol-5-yl]-2-methyl-4H-thieno[3,2-b]pyrrole-5-carboxylate was studied by X-ray analysis.