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The use of new 7-methylazolo[1,5-a]pyrimidine-6-carbonitriles for the construction of heterocyclic systems annulated at the pyrimidine ring has been demonstrated. Cascade cyclizations are carried out via the intermediate dimethylaminovinyl derivatives. The specific features of the cascade reactions with ammonia or aliphatic amines as N1 synthons, depending on the reaction conditions, are demonstrated. [ABSTRACT FROM AUTHOR]

The reaction 5-(arylmethylidene)-2,4,6-pyrimidine-2,4,6(1H,3H,5H)-triones with isoquinoline and dimethyl but-2-ynedioate gave cycloaddition products, mixtures of diastereoisomeric substituted dimethyl 2-aryl-2′,4′,6′-trioxo-1′,3′,4′,6′-tetrahydro-2H,2′H,11bH-spiro[pyrido[2,1-a]isoquinoline-1,5′-pyrimidine]-3,4-dicarboxylates which were converted to the corresponding dipotassium salts by treatment with excess potassium hydroxide in ethanol. The synthesized compounds are of interest as promising intermediate products with potential antitubercular and fungicidal activities. [ABSTRACT FROM AUTHOR]

The 1,3-dipolar cycloaddition reaction of ethyl (Z)-2-(2-methoxy-2-oxoethylidene)-7-methyl-3-oxo-5-aryl-2,3-dihydro-5H-thiazolo[3,2-a]pyrimidine-6-carboxylate and azomethine ylide which generated in situ by the reaction of isatin and 1,2,3,4-tetrahydroisoquinoline afforded novel 6′′-ethyl 2′-methyl-5′′-(aryl)-7′′-methyl-2,3′′-dioxo-6′,10b′-dihydro-2′H,3′′H,5′H,5′′H-dispiro[indoline-3,3′-pyrrolo[2,1-a]isoquinoline-1′,2′′-thiazolo[3,2-a]pyrimidine]-2′,6′′-dicarboxylate in moderate yields. The structures of all the products were characterized thoroughly by NMR, IR, HRMS together with X-ray crystallographic analysis. [ABSTRACT FROM AUTHOR]

Functionalization of α-aminopyridine to a new series of pyridine and fused pyridine derivatives has been achieved via its reaction with a variety of readily available reagents. Pyridines 2 and 3 were formed via reaction of amino derivative 1 with formamide and triethyl orthoformate. Hydrolysis of pyridine with 60% H2SO4 afforded 2-oxonicotinamide 6 in 44% yield. Intermolecular cyclization of pyridine 1 with ethyl cyanoacetate, diethyl malonate and malononitrile afforded pyrazolo[3,4-b]pyridine 8, pyrido[2,3-d]pyrimidine 9 and 1,8-naphthyridine 13 in moderate yields (63–76%). [ABSTRACT FROM AUTHOR]

In the presents work synthesis and characterization of new heterocyclic derivatives containing pyrazolo[3,4-d]pyrimidine linkage with 1,4-disubstituted-1,2,3-triazoles via methylene-oxy group. The selected synthesized compounds were tested for their in-vitro anticancer activity against various cancer cell lines. Synthesis of compounds was done under ultrasonic-assisted Huisgen 1,3-dipolar cycloaddition reaction with good yields. Some of the newly synthesized compounds demonstrated good to moderate anticancer activity, most of compounds shows activity against renal cancer cell lines. [ABSTRACT FROM AUTHOR]

An efficient synthesis and fluorescent properties of a new series of fused pyrimidine derivatives are described. Condensation of aminopyrimidine derivative 1 with acetophenone leads to olefinic pyrimidine 2, various addition-cyclization reactions of which give the corresponding bicyclic pyrimidines 4, 6, and 8. Cycloaddition reaction of pyrimidine 1 to benzoyl isothiocyanate gives thiourea derivative 9. Intramolecular cyclization of compound 9 with NaOH or Br2 produces pyrimidine derivatives 10 or 12, respectively. Heteroannulation of pyrimidine 1 with ninhydrin or α-carbonyl carboxylic acid 15 gives the tetracyclic pyrimidine 14 and diazepine derivative 18, respectively. Fluorescence properties of pyrimidine derivatives have been tested. [ABSTRACT FROM AUTHOR]

Cyclization of 1,2-diamino-4(4-chlorophenyl)-6-oxo-1,6-dihydropyrimidine-5-carbonitrile 2 with a variety of electrophilic reagents results in formation of a new series of pyrimidine heterocycles including pyrimidotriazepines, pyrimidotriazines and triazolopyrimidines. Some newly synthesized compounds are tested for their antibacterial activity against Gram-positive and Gram-negative bacteria. [ABSTRACT FROM AUTHOR]

Abstract: The synthesis and fluorescence properties of highly substituted bicyclic pryridine derivatives are described. 2-Substituted-4-oxo-pyrido[2,3-d]pyrimidines 2-8 resulted from the acylation reaction of α-aminonicotinonitrile 1 with aroyl chlorides, diethyl malonate, morpholine-4-carboxylate, acetic anhydride or formic acid under solvent-free conditions. [4 + 2] Cyclocondensation and cycloaddition reactions of compound type 1 with formamide and ammonium thiocyanate tolerated the fused pyrimidines 9 and 11, respectively. Finally, the Friedländer-like reaction was applied for the synthesis of 1,8-naphthyridines 12-15 via reaction of compound 1 with cyclohexanone, dimedone, acetyl acetone and benzyl methyl ketone, respectively, under AlCl3 catalysis. The fluorescence spectroscopic data of compounds 1-4, 6-8, 11, 12, 14 and 15 measured and significant results were observed.Graphical abstract: [ABSTRACT FROM AUTHOR]

A green metal-free synthesis of spiro-fused 3,4′-pyrazolo[4′,3′:5,6]pyrido[2,3-d]pyrimidine derivatives via deamination cyclization reactions of isatins, substituted 1H-pyrazol-5-amine, and 6-aminopyrimidine-2,4(1H,3H)-dione or 6-amino-1,3-dimethylpyrimidine-2,4(1H,3H)-dione in aqueous medium is reported. This is an efficient route for synthesis of the target products by deamination cyclization reaction. The other advantages of this process are high yield, easy separation, wide substrate range, and environmental friendliness. [ABSTRACT FROM AUTHOR]

In this work, we provide the first generalized and critical analysis of data on the chemistry of malononitrile dimer (2-aminopropene-1,1,3-tricarbonitrile) - a multifunctional reagent that is widely used for the preparation of diverse heterocyclic systems. The majority of references are from the last 20-25 years. [ABSTRACT FROM AUTHOR]

Reactions of pyrazolo[3,4-d]pyrimidine-containing hydrazines with pregnenolone derivatives were studied. The reaction of 16α,17α-epoxy-3β-hydroxy-5-pregnen-20-one and its 3-O-acetyl derivative with 6-hydrazino-3,4-dimethyl-1H-pyrazolo[3,4-d]pyrimidine and 4-hydrazino-3-methyl-6-phenyl-1H-pyrazolo[3,4-d]pyrimidine afforded new androsteno[17,16-d]pyrazoles with pyrazolo[3,4-d]pyrimidine fragments. The reaction of 3β-hydroxypregna-5,16-dien-20-one and its 3-O-acetyl derivative with 4-hydrazino-3-methyl-6-phenyl-1H-pyrazolo[3,4-d]pyrimidine gave hydrazones at position 20 of the pregnenolone molecule, which upon melting undergo cyclization to androsteno[17,16-d]-2′-pyrazolines. Reflux of the hydrazone in mesitylene in the presence of MCPBA leads to a mixture of three products, namely, androsteno[17,16-d]-2′-pyrazoline, androsteno[17,16-d]pyrazole, and dodecahydro-13H-phenanthro[1′,2′:5,6]pyrano[2,3-d]pyrazole derivative resulting from the oxidative expansion of the steroid cyclopentane ring D. [ABSTRACT FROM AUTHOR]

The review summarizes information on cyclopropane as an independent pharmacophore group and as a fragment for modification of pharmacological activity level of medicines used in practice. The advantages of a cyclopropane fragment over its bioisosteres are that, on the one hand, this fragment imposes conformational rigidity on the molecules of physiologically active compounds and, on the other hand, the replacement of acyclic terminal and “linker” groups with a cyclopropane fragment increases the metabolic stability of the target structures and extends the scope of their therapeutic action. [ABSTRACT FROM AUTHOR]

The cyclic amidine 3 was used as a precursor in this research, which was synthesized by chlorination of compound 1, followed by ring closure with hydrazine hydrate. Cyclization of amidine compound 3 with acetylacetone, ethyl cyanoacetate, chalcone analogue 6 and benzylidenemalononitrile ( 8) tolerated the expected tricyclic pyrimidines 4, 5, 7 and 9, respectively. Reaction of 3 with ammonium thiocyanate followed by cyclization of the product 10 with DMF, ethyl chloroformate and chloroacetyl chloride afforded triazine derivatives 11- 13, respectively. Nucleophilic substitution of the later compound with EtONa gave ethyl methyl ether derivative 14. The benzamide derivative 15 was obtained by reaction of 3 with benzoylisothiocyanate or benzoylation of compound 10 with benzoyl chloride. Finely, heterocylization of 15 in the presence of EtN gave the triazine derivative 16. Graphical abstract: 6-(4-Chlorophenyl)-4-(4-isopropylphenyl)-1 H-pyrazolo[3,4- b]pyridin-3-amine ( 3) was used as the starting material for the synthesis of pyrido[2′,3′:3,4]pyrazolo[1,5- a]pyrimidine and pyrido[2′,3′:3,4]pyrazolo[1,5- a][1,3,5]triazine derivatives via cycloaddition and intermolecular cyclization reactions. [ABSTRACT FROM AUTHOR]

The reaction of 4,6-dichloropyrimidine-5-carbaldehyde with cyanomethyltriphenylphosphonium chloride gave (2 Е)-3-(4,6-dichloropyrimidin-5-yl)acrylonitrile, which was further used for the preparation of 4,6-diamino-substituted pyrimidinylacrylonitrile derivatives, capable of intramolecular cyclization with the formation of new 4-amino-substituted 7-iminopyrido[2,3- d]pyrimidines. Performing the reaction with 4-amino-6-chloropyrimidine-5-carbaldehyde led to 7-amino-4-chloropyrido[2,3- d]pyrimidine, a promising intermediate for the synthesis of pyrido[2,3- d]pyrimidine-4,7-diamines. [ABSTRACT FROM AUTHOR]

5-Allylpyrimidine-4-ones react with arylsulfenyl chlorides in dichloromethane with the formation of 5-[(2-arylsulfanyl)-3-chloropropyl]-pyrimidine-4-ones that under the action of sodium acetate undergo cyclization into 6-arylsulfanyl-6,7-dihydro-5 H-pyrano[2,3- d]pyrimidines. At performing similar reactions in nitromethane an intramolecular electrophilic cyclization occurs affording 6-[(arylsulfanyl)methyl]-5,6-dihydrofuro[2,3- d]pyrimidines. [ABSTRACT FROM AUTHOR]

Iodination of 2-[allyl(methallyl)sulfanyl]-6-(trifluoromethyl)pyrimidin-4(3 H)-ones was accompanied by cyclization to 2,3-dihydro[1,3]thiazolo[3,2- a]pyrimidin-4-ium triiodides. 3-(Iodomethyl)-3-methyl- 7-oxo-5-(trifluoromethyl)-2,3-dihydro[1,3]thiazolo[3,2- a]pyrimidin-4-ium triiodide was reduced with sodium iodide to 3,3-dimethyl-7-oxo-5-(trifluoromethyl)-2,3-dihydro[1,3]thiazolo[3,2- a]pyrimidin-4-ium iodide. [ABSTRACT FROM AUTHOR]

A reaction of octa-1,7and deca-1,9-dienes with an excess of bromofluorocarbene proceeds predominantly with the formation of a monoadduct, whereas the bis-adduct can be prepared by repeated cyclopropanation. The [1+2] cycloaddition of dichlorocarbene to the monoadduct of bromofluorocarbene with deca-1,9-diene gave a new bis(cyclopropane) containing gem-dichloro- and gem-bromofluorocyclopropane fragments in one molecule. The bis-adducts obtained were subjected to the heterocyclization with nitronium triflate: in the case of bis( gem-bromofluorocyclopropane) the reaction proceeded with retention of one dihalocyclopropane fragment and gave mononuclear pyrimidine N-oxide. [ABSTRACT FROM AUTHOR]

A series of novel pyrimidines ( 6a-6i) has been synthesized from corresponding chalcones and isonicotinimidamide.HCl in the presence of potassium carbonate involving Michael addition followed by cycloaddition. All newly synthesised chalcones and pyrimidines were screened for in vitro antimicrobial activity against various Gram positive, Gram negative bacterial and fungal strains. Most of compounds displayed high antimicrobial activity compared to standard drugs Penicillin, Streptomycin and Ampothericin-B. [ABSTRACT FROM AUTHOR]

2-[Allyl(but-3-en-1-yl, pent-4-en-1-yl)sulfanyl]pteridin-4(3 Н)-ones at heating in polyphosphoric acid undergo an intramolecular cyclization affording respectively 9-methyl-8,9-dihydro-5 H-[1,3]thiazolo[3,2- a] pteridin-5-one and 10-methyl(ethyl)-9,10-dihydro-5 Н,8 Н-[1,3]thiazino[3,2- a]pteridin-5-ones of angular structure. The cyclization of 2-(alkenylsulfanyl)pteridin-4(3 Н)-ones under the action of iodine or arylsulfenyl chlorides afforded iodo(arylsulfanyl) derivatives of angularly fuzed thiazolo- and thiazinopteridines. [ABSTRACT FROM AUTHOR]

[Figure not available: see fulltext.] 3-Diazopyrrolidones, prepared by nitrosation of 3-aminopyrrolidones with isoamyl nitrite in the presence of glacial acetic acid, enter in a 1,3-dipolar cycloaddition reaction with dimethyl ester of acetylenedicarboxylic acid to form tetrahydropyrazolo[1,5- c]pyrimidines in good yields. [ABSTRACT FROM AUTHOR]

Enzymes of the phosphoribosyl pyrophosphate synthetase family (PRPPS, EC 2.7.6.1) catalyze the formation of 5-phosphoribosyl pyrophosphate (5-PRPP) from adenosine triphosphate and ribose 5-phosphate. 5-Phosphoribosyl pyrophosphate is an important intermediate in the synthesis of purine, pyrimidine, and pyridine nucleotides, as well as of the amino acids histidine and tryptophan. The crystallization conditions for E. coli PRPPS were found by the vapor-diffusion technique and were optimized to apply the capillary counter-diffusion technique. The X-ray diffraction data set was collected from the crystals grown by the counter-diffusion technique using a synchrotron radiation source to 3.1-Å resolution. The crystals of PRPPS belong to sp. gr. P622 and have the following unit-cell parameters: a = b = 104.44 Å, c = 124.98 Å, α = β = 90°, γ = 120°. The collected X-ray diffraction data set is suitable for the solution of the three-dimensional structure of PRPPS at 3.1-Å resolution. [ABSTRACT FROM AUTHOR]

2-(Ethoxymethylidene)-3-oxo carboxylic acid esters reacted with tetrazol-5-amine to give ethyl 4-alkyl-2-azidopyrimidine-5-carboxylates capable of undergoing subsequent nucleophilic substitution of hydrogen on C or azido group. The reaction of ethyl 2-benzoyl-3-ethoxyprop-2-enoate with tetrazol-5-amine was accompanied by partial decomposition to afford a mixture of ethyl 3-oxo-3-phenylpropanoate and ethyl 7-(1-ethoxy-1,3-dioxo-3-phenylpropan-2-yl)-5-phenyl-4,7-dihydrotetrazolo[1,5- a]pyrimidine-6-carboxylate. Ethyl 7-hydroxytetrazolo[1,5- a]pyrimidine-6-carboxylate was formed as a result of cyclization of diethyl 2-(ethoxymethylidene)propanedioate with tetrazol-5-amine. [ABSTRACT FROM AUTHOR]

Proceeding from 3-(4-methyl-6-oxo-2-phenyl-1,6-dihydro-5-pyrimidinyl)propanoic and 2-methylpropanoic acids by successive reactions of chlorination, amination, and heterocyclization 4-amino-substituted pyrimidines were synthesized: 5,6,7,8-tetrahydropyrido[2,3- d]pyrimidine derivatives and 4-methyl-2-phenyl-5,6-dihydrobenzo[4′,5′]imidazo[2′,1′:6,1]pyrido[2,3- d]pyrimidine which we had previously obtained by alternative method. Antibacterial properties of the synthesized compounds were studied. [ABSTRACT FROM AUTHOR]

A novel method has been developed for the synthesis of 8-alkyl[1, 2, 4]triazolo[5,1-b]purines from 6-nitro[1,2,4]triazolo[1,5-a]pyrimidin-7-ones via successive phosphoryl chloride-mediated chloro-desoxygenation, aminodehalogenation, and reduction to give 7-alkylamino-6-amino[1,2,4]triazolo-[1,5-a]pyrimidines. The latter can be cyclized in the presence of formic acid. [ABSTRACT FROM AUTHOR]

5-( P-tolyl)-2-[(3-bromo-4-methoxy benzylidene) hydrazino]-thiazole 3, 3-[(3-bromo-4-mehtoxy benzylidine) amino]-2-thiohydantion 5, and 4,6-disubstituted-3-[(3-bromo-4-methoxybenzyliden) amino]-2-thioxo pyrimidines 10 have been prepared via cyclization of 3-bromo-4-methoxy benzaldehyde thiosemicarbazone 2 with 4-methyl phenacyl bromide, ethyl chloroacetate, and dicarbonyl compounds in different conditions. Acetylation of 3 and 5 with acetic anhydride gave the corresponding monoacetyl derivatives 4 and 6, while the acetylation of 5 with acetic anhydride in the presence of fused sodium acetate gave diacetyl derivative 7. Condensation of compound 5 with benzaldehyde in the presence of piperidine yielded the corresponding 3-substituted-5-benzylindene 2-thiohydation 8. Acetylation of compound 8 with acetic anhydride gave the corresponding 1-acetyl-3-substituted-5-benzylidene-2-thiohydantion 9. The mass spectral fragmentation patterns of some prepared compounds are investigated in order to elucidate the structure of the synthesized nitrogen heterocycles. [ABSTRACT FROM AUTHOR]

New androsteno[17,16- d]pyrazoles and -pyrazolines with pyrazolo[3,4- d]pyrimidine fragments were synthesized. A reaction of 3β-hydroxypregna-5,16-dien-20-one and its 3-O-acetyl derivative with 6-hydrazino-3,4-dimethyl-1 H-pyrazolo[3,4- d]pyrimidine led to hydrazones at position 20 of the pregnenolone molecule, a possibility of their cyclization was studied. Upon melting, the hydrazones cyclize with the formation of pyrazoline ring annulated with ring D of the steroid at positions 16 and 17. Reflux of the hydrazones in mesitylene with AcOH leads to a mixture of two reaction products: androsteno[17,16- d]pyrazole and a dodecahydro-13 H-phenanthro[1′,2′:5,6]pyrano[2,3- d]pyrazole derivative. Apparently, this transformation proceeds through the corresponding epoxide with subsequent rearrangement, which leads to the ring D expansion. [ABSTRACT FROM AUTHOR]

A letter to the editor is presented regarding the two approaches in constructing the azolopyrimidine system such as by fusion of azole ring with the pyrimidine or cyclization of the pyrimidine ring on an azole.

Two variants are discussed for the synthesis of ethyl N-alkyl- N-(6-amino-5-formylpyrimidin-4-yl)-glycinate derivatives, which are converted by intramolecular cyclization under the influence of sodium methoxide to give methyl 7 H-pyrrolo[2,3-d]pyrimidine-6-carboxylates. New derivatives of pyrimido- [5',4':4,5]pyrrolo[2,1- c][1,4]oxazines containing 3-chloropropyl groups at position 8 have been prepared. [ABSTRACT FROM AUTHOR]

A method is presented for the synthesis of 4-(substituted phenyl)-3-(3-substituted phenyl)4 H-spiro[isoxazole-5,3′-pyrido[1,2- a]pyrimidine]-2′,4′-dione (3), 3-(4-substituted phenyl)-3 H-isoxazole[3, 4- d]pyrido[1,2- a]pyrimidin-4-(3a H)-one (4) and 3-(4-substituted phenyl) 3,3a-dihydropyrazolo[3,4- d]pyrido[1,2- a]pyrimidin-4-(2 H)-one (5) which consists of the conversion of 2 H-pyrido[1,2- a]pyrimidine-2,4(3 H)-dione (1) to chalcones (2) and their 1,3-dipolar cycloaddition with appropriate aldoximes to give spiro compounds and heterocyclization using amines to yield isoxazolines and pyrazolines. All the compounds were screened for their antimicrobial and antitubercular activity. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

Information relating to the synthesis of tetrahydropyrimidin-2(1 H)-ones(thiones), annelated at the N(1)-C(6) bond, by cascade cyclization of substituted N-(3-oxoalkyl)ureas and thioureas is classified. The general relationships of this process are presented. [ABSTRACT FROM AUTHOR]

Palladium-catalyzed cross-coupling reactions (Heck, Sonogashira, Stille, Suzuki) in the pyrrolo-[2,3- d]pyrimidine series with emphasis on synthesis of biologically active and functional materials are reviewed. [ABSTRACT FROM AUTHOR]

A reaction of 2-diaminomethylidenedimedone with aryl isocyanates leads to the formation of the corresponding ureas, which upon the action of sodium methoxide cyclize to 4-amino-7,8-dihydroquinazoline-2,5(1 H,6 H)-dione derivatives. The latter react with aryl isocyanates following the similar scheme to furnish 1,6-diaryl-8,8-dimethyl-7,8-dihydro-1 H-pyrimido-[4,5,6- de]quinazoline-2,5(3 H,6 H)-diones, new tricyclic compounds containing pyrimidopyrimidine fragment. [ABSTRACT FROM AUTHOR]

Condensation of ethyl ethoxymethyleneacetoacetate and ethyl ethoxymethylenecyanoacetate in ethanol with 3-substituted 3-aminopyrazoles and 5-amino-1,2,4-triazole gave the 2-substituted 6-ethoxy- carbonyl-7-methyl- and 7-amino-6-ethoxycarbonylpyrazolo[1,5-a]pyrimidines as well as 7-amino-6-ethoxycarbonyl-1,2,4-triazolo[1,5-a]pyrimidine. In the presence of alkali these rearranged to 2-substituted 6-acetyl-7-hydroxy- and 6-carbamoyl-7-hydroxypyrazolo[1,5-a]pyrimidines respectively and also to 6-carbamoyl-7-hydroxy-1,2,4-triazolo[1,5-a]pyrimidine. According to H (including NOESY) NMR spectroscopic data there were formed, along with the cyclization products, noncyclic condensation adducts (as cyano derivatives) from ethyl ethoxymethylenecyanoacetate with 5-aminopyrazoles. In the presence of alcoholic alkaline solution these were also transformed in high yield to 6-carbamoyl-7-hydroxypyrazolopyrimidines. When refluxed for a longer time in 12% aqueous alcoholic alkaline solution the 6-ethoxycarbonyl-2,7-dimethylpyrazolo[1,5-a]pyrimidine and 6-acetyl-7-hydroxy-2-methylpyrazolo[1,5-a]pyrimidine recyclize to give 6-carboxy-2,7-dimethyl- and 2,7-di- methylpyrazolo[1,5-a]pyrimidines. [ABSTRACT FROM AUTHOR]

The article offers information on the types of isomerizational recyclization in various pyridine, pyrimidine and pyrazine systems. It states that a recyclization scheme includes the attack of nucleophilic part, opening of the pyrimidine ring, subsequent cyclization that involves the exocyclic nitrogen atom of nitroso group. It discusses the rearrangement of 5,7-dihydroxy-2-methyl-3,6-dinitosopyrazolo[1,5-a]pyrimidine to 5-hydroxy-2-methyl-3-nitrosopyrazolo[1,5-b] [1,2,4] triazine.

method for the synthesis of new 8-amine derivatives of pyrano[4",3":4',5']pyrido[3',2':4,5]furo-[3,2- d]pyrimidines based on 6-oxo derivatives of pyrano[3,4- c]pyridines has been developed. [ABSTRACT FROM AUTHOR]

Novel photoadducts were obtained by irradiation of thioinosine (6-thiopurine riboside, TI) in deaerated aqueous solution without and in the presence of uridine and adenosine. Excitation (λ> 300 nm) of TI to its excited S2state yields a single bimolecular photoproduct. It is a purine–pyrimidine diriboside in which the purine ring is attached to the amide nitrogen of 6-amino-4-thioxo-5-formamidopyrimidine. When TI was irradiated in the presence of an excess of adenosine, two photoproducts were isolated: diribosides of N-(4,6-diaminopirymidin-5-yl)-N-formyl-6-aminopurine and N-(4-amino-6-formylamino-pyrimidin-5-yl)-6-aminopurine, both containing a purine and a formylaminopyrimidine (Fapy) fragment. The photoreaction of TI with uridine gave two regioisomeric photoproducts identified as diribosides containing either 5- or 6-(purin-6-yl)uracil as aglycones. A multistep mechanism leading to the stable photoproducts is proposed. In the first step of the mechanism, the CS group of the excited TI undergoes a [2 + 2] cycloaddition regioselectively to the N(7)C(8) bond of the purine ring or adds in a non-regioselective manner to the C(5)C(6) bond of uracil. The unstable photoproducts thus formed undergo a series of dark reactions at room temperature. The photocycloaddition reactions originate from the excited T1state of TI. This conclusion is supported by a combination of evidence from reaction quenching studies using both steady-state quantum yield determinations and kinetics results from nanosecond laser flash photolysis. The T1state of TI is quenched by other TI molecules in their S0state (self-quenching) and also by uridine and adenosine, all with large rate constants (0.8–5) × 109M−1s−1. The quantum yields of the reactions are in general very low (R≤ 8 × 10−3). The sources of the inefficiency in the photocycloaddition of TI to uridine and adenosine are discussed. The photoproducts containing the Fapy residue undergo deformylation and isomerization of the ribosyl moiety (anomerization, furanose/pyranose transformation) upon heating in aqueous solution. Products of the transformations were identified. [ABSTRACT FROM AUTHOR]

Pyridoannulation of 5-ethoxycarbonyl-4-methylpyrimidine and 7-methyl-6-ethoxy-carbonyl[1,2,4]triazolo[1,5- a]pyrimidine derivatives has been studied. [ABSTRACT FROM AUTHOR]

Ethyl 2-ethoxymethylidene-3-polyfluoroalkyl-3-oxopropionates under mild conditions undergo regioselective condensation with urea at the ethoxymethylidene substituent giving rise to ethyl 3-polyfluoroalkyl-3-oxo-2-(ureidomethylidene)propionates. Under more drastic conditions, the latter cyclize at the fluoroacyl fragment to form ethyl 4-polyfluoroalkyl-4-hydroxy-2-oxo-1,2,3,4-tetrahydropyrimidine-5-carboxylates. [ABSTRACT FROM AUTHOR]

Fluorine-containing quinazolines annulated at the sides [ a] and [ c] were synthesized by the reaction of 2- and 4-hydrazino-substituted quinazolines with aldehydes and subsequent oxidative cyclization. Annulation at the side [ b] was performed by alkylation of 2-alkylthio-4(3 H)-quinazolinones with bromoethanol and ipso-substitution of the alkylthio group. [ABSTRACT FROM AUTHOR]

Available polycentral unsaturated azlactones with 4-dichloromethylene group by successive treating with benzamidine and then with morpholine or its analogs were converted to substituted 5-acylamino-4-hydroxypyrimidines containing the residues of the corresponding nitrogen bases in the position 6. The structure of these cyclization products is consistent with the scheme of their preparation and has been confirmed also by 1H NMR spectroscopy and XRD analysis. [ABSTRACT FROM AUTHOR]

Heteroarylcoumarins containing 2-indole, 3-pyrazole, and 4-pyrimidine substituents in the 6-position of the coumarin ring were synthesized. [ABSTRACT FROM AUTHOR]

Published data on the recyclization reactions of 1,3,5-triazines are reviewed. The classification is based on the fragments of the 1,3,5-triazine molecules used in the construction of new heterocycles. [ABSTRACT FROM AUTHOR]

6-Allylsulfanyl-1-arylpyrazolo[3,4- d]pyrimidin-4(5 H)-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(5 H)-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(5 H)-ones with sulfuric acid. [ABSTRACT FROM AUTHOR]

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(1 H)-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. [ABSTRACT FROM AUTHOR]

Structural modification of some (pyrimidin-2-yl)hydrazones derived from ethyl acetoacetate via methylation at the N3 atom promotes anomalous cyclization to give [1,2,4]triazolo[1,5- a]pyrimidine derivatives. The mechanism of this transformation includes specific cleavage of the aliphatic fragment in the substrate with subsequent rearrangement of carbene-like intermediate. [ABSTRACT FROM AUTHOR]

The previously unknown three component condensation of hetarylguanidines, orthoesters, and active methylene carbonyl compounds has been studied. Depending on the nature of the latter products of both linear combination and subsequent cyclizationl leading to pyrimidine or tetrahydroquinazoline structures were obtained. [ABSTRACT FROM AUTHOR]

Cyclization of 1-(2,4-dioxo-1,2,3,4-tetrahydropyrimidin-6-yl)carbonyl-4-R-thiosemicarbazides in basic medium gave 6-(4-R-5-thioxo-1,2,4-triazol-3-yl)pyrimidine-2,4-diones (R = Allyl, Ph). Alkylation of the latter with iodomethane occurred at the sulphur atom to give the corresponding methylsulfanyl derivatives. Acetylation using acetyl chloride occurred at the N(1) atom of the triazole ring to the corresponding acetyl derivative when R = Ph but for R = Allyl the acetylation did not occur under the same conditions. In the presence of bromine in refluxing methanol the indicated allyl-substituted compound cyclizes to 6-bromomethyl-3-(2,4-dioxo-1,2,3,4-tetrahydropyrimidin-6-yl)-5,6-dihydrothiazolo[2,3-c]-1,2,4-triazole. Under Mannich and bromination conditions the methylsulfanyl derivatives prepared form derivatives at the 5 position of the uracil ring: 5-methylmorpholino-(piperidino)-and 5-bromo-(4-R-5-thioxo-1,2,4-triazol-3-yl)pyrimidine-2,4-diones respectively. [ABSTRACT FROM AUTHOR]

Data on the isomerization recyclizations of pyrimidines, particularly the Kost-Sagitullin and other transformations accompanied by substitution of an endocyclic atom in pyrimidine by an extracyclic nitrogen or carbon atom (N-N, N-C, or C-C recyclizations), are summarized and analyzed. Data from research on the Kost-Sagitullin and certain other isomerization transformations of pyrimidines at the Institute of Organic Chemistry, National Academy of Sciences of the Republic of Armenia, in recent years are presented. [ABSTRACT FROM AUTHOR]

Products of additive cyclization with ring closure at the nitrogen atom of the thiohetaryl unit were synthesized by the interaction of 4,6-dimethylpyrimidine-2-, 3-cyano-4,6-dimethylpyridine-2-, quinoline-8-, and 1,3-benzothiazole-2-sulfenyl chlorides with 3,3-dimethyl-1-butene. [ABSTRACT FROM AUTHOR]

It has been shown that 1-aryl-8-(4-bromophenyl)-4,6-dioxo-2H(phenyl)-7-phenyl-1,4,6,7,8,9-hexahydropyrimido[4,5-b][1,6]naphthyridines are formed on heating anilides of 1-aryl-7-(4-bromostyryl)-4-oxo-1,4-dihydropyrido[2,3-d]pyrimidine-6-carboxylic acids in PPA. [ABSTRACT FROM AUTHOR]