Stabilization of even-electron ions by cyclization of substituents on 3N- and 4N-nitrogens in 4N-substituted cytosines

Electron impact mass spectra of 4N-substituted derivatives of cytosine are reported. The strong influence of 4N-substituents on the mode of mass fragmentation occurring upon electron impact ionization was proved. The presence of α-carbon in the 4N-substituent extends the possibilities of fragmentation via rearrangement leading to formation of even-electron bicyclic ions containing quaternary 3N-nitrogen. When β-carbon was present in the 4N-substituent, the decomposition based on elimination of alkenes was detected as well as the rearrangement leading to formation of bicyclic even-electron ions containing quaternary 3N- or 4N-nitrogen.     

Thioureas from 3-aminoquinazolin-4(3H)-one. 2. Unusual alkaline recyclization of 3-(N",N",S-trialkylisothioureido)quinazolin-4(3H)-ones into new 1,3,4-oxadiazoles

3-(N",N",S-trialkylisothioureido)quinazolin-4(3H)-ones obtained by the reactions of 3-(N",N"-dialkylthioureido)quinazolin-4(3H)-ones with alkyl halides undergo unusual recyclization into 5-(2-aminophenyl)-2-dialkylamino-1,3,4-oxadiazoles under the action of aqueous solutions of alkali, hydrazine, and primary aliphatic amines. A plausible mechanism of the recyclization was proposed.     

Chemistry of coumarins. Thermal reactions of 4-chloro-3-coumarinyl N,N-dialkyldithiocarbamates and 3-nitro-4-coumarinyl N-phenyldithiocarbamate

The thermal reactions of 4-chloro-3-coumarinyl N,N-dialkyldithiocarbamates 2–4 and 3-nitro-4-coumarinyl N-phenyldithiocarbamate, 9 , afforded the novel heterocyclic systems, e.g. bis-6H-1-benzopyrano[4,3-b]1,4]dithiin, 7 , and bis-6H-1-benzopyrano[4,3-b][1,4]thiazine, 14. A possible mechanism of the formation of the reaction products is discussed.     

A facile synthesis of 3-substituted 2-cyanoquinazolin-4(3H)-ones and 3-alkyl-2-cyanothieno[3,2-d]pyrimidin-4(3H)-ones via 1,2,3-dithiazoles

The reaction of methyl anthranilate with 4,5-dichloro-1,2,3-dithiazolium chloride (Appel's salt) in the presence of pyridine (2 equivalents) in dichloromethane at room temperature gave methyl N-(4-chloro-5H-1,2,3-dithiazol-5-ylidene)anthranilate ( 3a ) (50% yield), which reacted with sterically less hindered primary alkylamines to give directly 3-alkyl-2-cyanoquinazolin-4(3H)-ones 5 in moderate to good yields. With tert-butylamine, N-(2-methoxycarbonylphenyl)iminocyanomethyl N-(tert-butyl) disulfide 7 and methyl 2-(N-cyanothioformamido)anthranilate ( 8 ) were isolated in 33% and 59% yields, respectively. The cyano group of quinazoline 5a (R = CH₃) is readily displaced by various nucleophiles to give 2-substituted quinazolinones 11–19 , which indicates that compounds 5 can be utilized as starting materials for the synthesis of new 2-substituted quinazolines. Similarly 3-alkyl-2-cyanomieno[3,2,-d]pyrimidin-4(3H)-ones 22 were prepared from methyl 3-[N-(4-chloro-5H-1,2,3-dimiazol-5-ylidene)]-2-thiophencarboxylate ( 21 ) in moderate to good yields.     

Die neuen Schichtsilicate Ba3Si6O9N4 und Eu3Si6O9N4

The New Layer‐Silicates Ba₃Si₆O₉N₄ and Eu₃Si₆O₉N₄ The new oxonitridosilicate Ba₃Si₆O₉N₄ has been synthesized in a radiofrequency furnace starting from BaCO₃, amorphous SiO₂ and Si₃N₄. The reaction temperature was at about 1370 °C. The structure of the colorless compound has been determined by single‐crystal X‐ray diffraction analysis (Ba₃Si₆O₉N₄, space group P3 (no. 143), a = 724.9(1) pm, c = 678.4(2) pm, V = 308.69(9)· 10⁶ pm³, Z = 1, R1 = 0.0309, 1312 independent reflections, 68 refined parameters). The compound is built up of corner sharing SiO₂N₂ tetrahedra forming corrugated layers between which the Ba²⁺ ions are located. Substitution of barium by europium leads to the isotypic compound Eu₃Si₆O₉N₄. Because no single‐crystals could be obtained, a Rietveld refinement of the powder diffractogram was conducted for the structure refinement (Eu₃Si₆O₉N₄, space group P3 (no. 143), a = 711.49(1) pm, c = 656.64(2) pm, V = 287.866(8) ·10⁶ pm³, R_p = 0.0379, R_F² = 0.0638). The ²⁹Si MAS‐NMR spectrum of Ba₃Si₆O₉N₄ shows two resonances at ?64.1 and ?66.0 ppm confirming two different crystallographic Si sites.     

Synthesis of 3-N-acetyl-N-arylaminoacetyl-4-ethoxycarbonyl-5-methylpyrazoles

The acetylation of 2-N-arylaminomethylene-4-ethoxycarbonyl(or acetyl)-5-melhyl-3(2H)furan-ones produces N-acetylated compounds which react with hydrazine to yield substituted pyrazoles.     

Ozonides of N-acyl-4-phenyl-3a,4,5,9b-tetrahydro-3H-cyclopenta [c]quinoline

Ozonation of N-acyl-4-phenyl-3a,4,5,9b-tetrahydro-3 H-cyclopenta[ c]quinoline gave stable ozonides: a conformationally mobile isomer with the pseudoequatorial N-acyl group and a conformationally stable isomer with the pseudoaxial N-trifluoroacetyl group.     

Mass spectral fragmentation pattern of 3-methyl- and 3-phenyl-4-(N-methylarylhydrazono)isoxazol-5-ones

3-Methyl-4-(N-methylarylhydrazono)isoxazol-5-ones and 3-phenyl-4-(N-methylarylhydrazono)isoxazol-5-ones undergo considerable fragmentation on electron impact involving rupture of the isoxazolone ring and bonds in the N-methylarylhydrazono side chain.     

Meso-ionic compounds. XI,photochromic 4-halogeno-3-(3-pyridyl)sydnones

Halogenation of 3-(3-pyridyl)sydnone with N-halosuccinimides in chloroform afforded the 4-halogeno-3-(3-pyridyl)sydnones where X = CI, Br, I. The 4-chloro- and 4-bromopyridylsydnones were photochromic. 3-(3-Pyridyl)sydnone was obtained in both high yield and purity by dehydration of N-nitroso-N-(3-pyridyl)glycine with trifluoroacetic anhydride.     

A Short and Efficient Synthesis of (3S,4S)-1-Benzyl-4-N-Benzylamino-3-Hydroxypiperidine

(3S,4S)-1-Benzyl-4-N-benzylamino-3-hydroxypiperidine 1 was efficiently synthesized from (S)-pyroglutaminol.     

Photochemical methoxy/hydroxymethyl rearrangement in 3-methoxy-N-substituted-4-pyriclones

N-Substituted 3-methoxy-4-pyridones Ia-e rearrange to the corresponding N-substituted 3-hydroxymethyl-4-pyridones IIa-e when irradiated at 254 or 300 nm in benzene or toluene solution.     

Polyazanaphthylene nucleosides II. Synthesis of β-D-ribofuranosyl derivatives of 4-quinazolone

The preparation of N¹ (2,3-O-isopropylidene-β-D-ribofuranosyl)-4-quinazolone ( 6 ) and N³-β-D-ribofuranosyI-4-quinazolone ( 3b ) are reported. The N³ derivative was prepared by the direct condensation of 4-trimethylsilyloxyquinazoline ( 2 ) and 2,3,5-tri-O-benzoyl- D - ribofuranosyl bromide. The N¹ derivative was prepared from the previously reported N¹ -β-D-ribofuranosyl-2,4-quinazolinedione via the cyclonucleoside 4 .     

New route to N-aryl and N-heteroaryl derivatives of 4-hydroxy-3-quinolinecarboxamides

The synthesis of N-aryl and N-heteroaryl substituted 4-hydroxy-3-quinolinecarboxamides 1 is described. The attack of dianions 12 of N-aryl substituted acetamides on the C-4 carbonyl of 4H-3,1-benzoxazin-4-ones 11 gave rise to ketoamides 13 , which smoothly cyclised in the presence of bases to afford quinolinecarboxamides 1 . By this method, a large number of 2-substituted 4-hydroxyquinolinecarboxamides can be prepared.     

Reaction of ketenes with N,N-disubstituted α-aminomethyleneketones. X. Synthesis of N,N-disubstituted 6-alkyl-4-amino-3,3-dichloro-3,4-dihydro-2H-pyran-2-ones and of 6-alkyl-4-amino-3-chloro-2H-pyran-2-ones

Cycloaddition of dichloroketene to N,N-disubstituted 1-amino-4-methyl-1-penten-3-ones and 1-amino-4,4-dimethyl-1-penten-3-ones occurred in moderate to fair yield only in the case of aromatic N-substitution to give N,N-disubstituted 6-alkyl-4-amino-3,3-dichloro-3,4-dihydro-2H-pyran-2-ones, which were dehydrochlorinated with DBN to afford in good yield N,N-disubstituted 6-alkyl-4-amino-3-chloro-2H-pyran-2-ones. In the case of aliphatic N,N-disubstitution, cyclo-addition led directly to 6-alkyl-4-dialkylamino-3-chloro-2H-pyran-2-ones only for N,N-disubstituted 1-amino-4,4-dimethyl-1-penten-3-ones. The reaction between 1-dimethylamino-4-methyl-1-penten-3-one and dichloroketene gave 3-chloro-4-dimethylamino-3,6-dihydro-6-isopropylidene-2H-pyran-2-one in low yield.     

Herstellung enantiomerenreiner Derivate von 3-Amino- und 3-Mercaptobuttersäure durch SN2-Ringöffnung des β-Lactons und eines 1,3-Dixoanons aus der 3-Hydroxybuttersä ure

Preparation of Enantiomerically Pure Derivatives of 3-Amino- and 3-Mercaptobutanoic Acid by S_N2 Ring Opening of the β-Lactone and a 1,3-Dioxanone Derived from 3-Hydroxybutanoic Acid From (S)-4-methyloxetan-2-one ( 1 ), the β-butyrolactone readily available from the biopolymer ( R )-polyhydroxybutyrate (PHB) and various C, N, O and S nucleophiles, the following compounds are prepared:(s)-2-hydroxy-4-octanone ( 3 ), (R)-3-aminobutanoic acid ( 7 ) and its N-benzyl derivative 5 , (R)-3-azidobutanoic acid ( 6 ) (R)-3-mercaptobutanoic acid ( 10 ), (R)-3-(phenylthio)butanoic acid ( 8 ) and its sulfoxide 9 . The (6R)-2,6-dimethyl-2-ethoxy-1,3-dioxan-4-one ( 4 ) from (R)-3-hydroxybutanoic acid undergoes S^N2 ring opening with benzylamine to give the N-benzyl derivative (ent- 5 ) of (S)-3-aminobutanoic acid in 30?40% yield.     

Tautomerism and electron impact mass spectra of pyrimidin-4(3H)- and -4(1H)-ones

A mass spectrometric identification and differentiation of pyrimidin-4(3H)- and -4(1H)-ones was carried out. N-Substitution at position 1 or 3 made the distinction of the two sets of compounds very easy because of their characteristic fragmentation pathways. Most interesting were the spectra of the N-unsubstituted derivatives, which illustrated a predominance of the two possible NH tautomers in relation to the 4-hydroxy structure.     

The preparation of 3-hydrazino-4-hydroxy- and 3-hydrazino-4-methoxypyridine from sydnones

3-Hydrazino-4-hydroxy- and 3-hydrazino-4-methoxypyridines, which could not be obtained by reduction of the corresponding diazonium salts, have seen prepared by decomposition of N-(4-substituted-pyrid-3-yl)-syndones.     

Fabrication of novel Ag/g-C3N4 electrode for resveratrol sensors

Ag/g-C₃N₄ is fabricated and used as an electrode for determining trans-resveratrol concentration. The compositional and structural characteristics of the as-fabricated Ag/g-C₃N₄ are studied through X-ray diffraction, transmission electron microscopy, and energy dispersive spectroscopy. Additionally, the electrochemical behavior of Ag/g-C₃N₄ is investigated using cyclic voltammetry. According to the experimental results, 1 wt%Ag/g-C₃N₄ exhibits an oxidation peak at 0.48 V, with a low detection limit (1.88 × 10⁻⁷ M) and satisfactory correlation coefficient (0.9975), suggesting that the proposed Ag/g-C₃N₄ electrode can be successfully used for detecting trans-resveratrol.     

Synthesis and reactions of 3-iodo-4H-pyran-4-ones

3-Iodo-4H-pyran-4-ones have been synthesised in excellent yield by the reaction of acetylenic β-diketones with iodine monochloride and were converted into the corresponding 4H-pyran-4-thiones. The iodopyrones and thiopyrones gave with methylamine the respective N-methylpyridones and thiopyridones. The structure of the above compounds was confirmed from their spectral characteristics.     

The synthesis of azahomotryptophane derivatives. The transformation of N-trifluoroacetyl-5-bromo-4-oxonorvaline methyl ester into 4-(imidazo[1,2-a]azinyl-3)-4-oxohomoalanine derivatives

Azatryptophane homologues, 4-(imidazo[1,2-a]pyridinyl-3)- 9a-9f and 4-(imidazo[1,2-a]pyrimidinyl-3)-4-oxohomoalanine derivatives 9g-91 , were prepared from N,N-dimethyl-N′-(pyridinyl-2)- 6a-6f and N,N-dimethyl-N-(pyriniidinyl-2)formamidines 6g-6i , and (S)-N-trifluoroacetyl-5-bromo-4-oxonorvaline methyl ester ( 2 ) and its (R,S)-isomer.