Tautomerism in malonic ester derivatives of s-triazine

Pmr and uv spectra of tris-, bis- and monomalonic ester derivatives of s-triazine were studied in chloroform, dioxane, methanol, water, acetonitrile, dimethylsulfoxide, dimethylformamide, and cyclohexylamine. The results indicate that the enaminic structures (I, II and III) predominate in chloroform, dioxane, methanol and water. A small amount of enolate is present in acetonitrile and a larger amount of enolate is present in dimethylsulfoxide, dimethylformamide and cyclohexylamine in the case of the tris- and bismalonic ester derivatives of s-triazine. The conclusion is reached that for these latter compounds in basic solvent, a tautomeric equilibrium exists between the enaminic form and resonance-stabilized enolate ions.     

均三嗪衍生物的合成及光谱性质研究

以乙腈、乙醇、氯化氢、冰乙酸等为原料,用苯作溶剂,制得三甲基均三嗪,再分别与α-萘甲醛、β-萘甲醛反应,得目标产物2,4,6-三(1-萘乙基)均三嗪、2,4,6-三(2-萘乙基)均三嗪衍生物,用IR,MS(MALDI-TOF),氢谱等现代分析手段确认目标化合物的结构,研究目标化合物的紫外吸收光谱、荧光光谱等性质。为均三嗪衍生物光电性能的开发利用提供新的功能材料和理论基础。     

Electrochemical transformations of cycloheptatriene derivatives

Redox reactions of a series of substituted cycloheptatrienes are studied on a platinum electrode in acetonitrile using the cyclic voltammetry method. It was found that heptaphenyl-substituted cycloheptatrienes are irreversibly oxidized in two stages in the range of high anodic potentials to form unstable radical cations and dications. As opposed to the unsubstituted and monosubstituted cycloheptatrienes, they are not reduced at the potentials higher than ?2 V (SCE). A new stable radical anion was found in the reduction of N-cycloheptatrienylphthalimide. Its spin density distribution is studied by ESR spectroscopy.     

A DNA-electrochemical biosensor for screening environmental damage caused by s-triazine derivatives

An electrochemical DNA-biosensor has been used to investigate the interactions between DNA and members of a group of ten derivatives of 1,3,5-triazine herbicides: chloro-s-triazines (atrazine, propazine, terbutylazin, and cyanazin), thiomethyl-s-triazines (ametryn, prometryn, terbutryn, and simetryn), and methoxy-s-triazines (prometon and terbumeton). A UV spectrophotometric study of this group of herbicides was also undertaken. Of this group only cyanazin could be oxidized in aqueous solution using a glassy carbon electrode. Use of the electrochemical DNA-biosensor revealed the occurrence of a time-dependent interaction of all the herbicides with DNA, via the appearance of guanine, guanosine, and adenosine oxidation signals that correspond to DNA damage. Adduct formation between the herbicide and the DNA purine bases guanine and adenine is suggested as a mechanism.     

Synthesis and transformations of furan derivatives

Condensation of thiosemicarbazones of furfural, 3-(2-furyl)acrolein, as well as their 5-nitro derivatives with chloroacetone by boiling in alcohol or acetic acid gives the corresponding 4-methylthiazolyl-(2)hydrazones. 4-Methylthiazolyl-(2)-hydrazones of 5-nitro-2-acetylfuran and 5-nitro-2-furfurilydeneacetone can be prepared by condensing the corresponding thiosemicarbazones with chloroacetone by heating with glacial acetic acid containing fused sodium acetate.For Part IV see [1].     

Some transformations of gibberellic acid derivatives

Conclusions A study was made of the oxidation of the hydroxyl group in gibberellic acid and its ester and of some of the reactions of the formed, -unsaturated ketones.     

Synthesis and transformations of pyrimidine derivatives

A methoxyl group in the 4 and 6 positions has a passivating effect on the ability of the methyl group in monomethoxymethylpyrimidine derivatives to enter into azo coupling; at the same time, a methoxyl group in the 2 position does not have an appreciable effect on the activity of the methyl group because the conjugation effect of the methoxyl group in this position is less than in the 4 and 6 positions.See [1] for Communication XVIII.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp. 1573–1574, November, 1970.     

Correlations between conformational isomerism and chromatographic diastereoselectivity of bis amino amide s-triazine derivatives

NMR spectroscopy was used to probe the conformational behavior of diastereomeric s-triazine derivatives containing two chiral amino amide substituents, in order to shed light onto the mechanism of chromatographic diastereoselectivity. Utilizing the amino hydrogen signals in the proton NMR spectrum, the population of the conformations caused by rotation about the bond between the amino nitrogen and aromatic carbon atoms could be observed. The population distribution between the three possible conformations was similar but not identical between the two diastereomers, with similar trends being observed for both bis alanine amide and bis valine amide derivatives. Based on a simple model in which it is assumed that adsorption to the hydrophobic RP-LC stationary phase occurs only for the conformations having both amino amide R-groups on the same side of the triazine ring plane, the different conformation populations between the two diastereomers obtained by NMR was consistent with the observed RP-LC elution order (L-L diastereomer followed by L-D). The predicted diastereoselectivity values from NMR data were compared to RP-LC diastereoselectivity values obtained using both C18 and polymeric columns, with both acetonitrile/water and DMSO/water mobile phases. Values obtained with the polymeric column were in better agreement with calculated values than those obtained with the C18 column, suggesting that the simple adsorption model used to calculate the diastereoselectivity is more relevant towards a simple hydrophobic polymeric surface rather than a more complex C18 stationary phase. This study indicates that proton NMR is a useful tool for studying the diastereoselective mechanism of these derivatives, due to the relatively slow C-N bond rotation caused by the significant sp(2) character of the amino nitrogen atoms.     

Heterogeneous photocatalytic synthesis of ammonia from water and nitrogen

Photocatalytic synthesis of ammonia from water and nitrogen was performed. Binary wafered catalysts prepared with semiconductor powder (TiO₂, SrTiO₃, CdS or GaP) and platinum black, where the copolymer of ethylene and vinylalcohol was used as a binder, were found to be more effective to yield ammonia than the semiconductor powders alone.     

Chemical transformations of benzyl derivatives of zirconium

Conclusions Exchange of the -benzyl ligands in the complexes [Cp₂ZrCH₂Ph]₂O, Cp₂Zr(CH₂Ph)₂, and (PhCH₂)₄,Zr was effected by treatment with various reagents, containing a labile H atom. When [Cp₂ZrCH₂C₆H₅]₂O is reacted with phenol the benzyl ligand exchanges for the phenoxy group without destroying the Zr-O-Zr bond, and also the mixed complex Cp₂Zr(OC₆H₅)(CH₂C₆H₅) is formed, with retention of the -benzyl ligand.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 3, pp. 705–707, March, 1984.     

Acid-catalyzed transformations of diepoxy derivatives of terpinolene

Transformations of diepoxy derivatives of terpinolene under conditions of homogeneous and heterogeneous acid catalysis were studied. Qualitative and quantitative compositions of the reaction mixtures were found to depend on the acidity of the medium and mutual orientation of the epoxide rings in the p-menthane skeleton. The experimental data were compared with the results of computer simulation of the most probable transformation pathways in terms of molecular mechanics and quantum-chemical methods.     

Chemical transformations of mackinazolinone and its derivatives

The thioanalog of mackinazolinone (2,3,4,10-tetrahydro-1 H-pyrido[2,1-b]quinazolin-10-one) was synthesized for the first time by reacting it with P₂S₅. The thioanalog was reacted with aromatic aldehydes and Vilsmeier- Haack reagent (DMF + POCl₃) to produce 4-arylidene- and -hydroxymethylidenemackinazolinthiones, respectively. The reactions of 4-hydroxymethylidenemackinazolinone with isomeric aminophenols and aminobenzoic acids and of hydroxymethylidenemackinazolinthione with thionylchloride were studied. Subsequent reaction of the obtained 4-chloromethylidene derivative with sodium hydroselenide was synthesized a new Se-containing derivative of mackinazolinone. It was shown that 4-formylmackinazolinthione existed in the enol form whereas 4-formylmackinazolinone existed as the enaminoaldehyde tautomer.     

Possible factors influencing the separation mechanism of diastereomeric amino acid derivatives obtained from s-triazine type reagents

Diastereomeric derivatives prepared from an amino acid and an amino amide using trichloro s-triazine as a coupling platform are known to produce good chromatographic diastereoselectivity for many amino acid analytes. The chromatographic diastereoselectivity of these derivatives is difficult to rationalize based on the possibility of four possible conformational isomers, which can interconvert by rotation about the C-N bonds between the amino substituents and the triazine ring. The observed diastereoselectivity implicates an unobvious but significant driving force which causes one of several conformations to be favored over the others. Several possibilities are discussed. Intramolecular hydrogen bonding between acid and amide substituents was explored using computer aided molecular modeling. While such hydrogen bonding may be geometrically possible between the amino acid and the amide substituents, it does not explain why derivatives produced from other chiral compounds which are not capable of the same hydrogen bonding interaction nevertheless exhibit substantial diastereoselectivity. Two other more general effects, steric hindrance to solvation and ion pairing, are therefore suggested as possible contributing factors to the chromatographic diastereoselectivity. Based on the conformational equilibrium behavior of related triazine compounds as reported in the literature, either one of these effects could influence the conformation of the diastereomeric derivatives even in the absence of intramolecular hydrogen bonding interactions between the two chiral substituents, and these effects may therefore be a contributing factor for the observed elution order of the diastereomers.     

Large second-order optical nonlinearities of s-triazine derivatives: View from micro molecules to macro crystals

Organic nonlinear optics (NLO) is also called mo-lecular nonlinear optics. In recent years organic mate-rials have been intensively studied because of their large NLO coefficients and structural diversities[1―3]. Second harmonic generation (SHG) is a bas…     

Heterogeneous photocatalytic reduction of NO in the presence of conjugated polymers

The reaction of NO with NH₃ is photocatalytic in the presence of poly(p-phenylene), polythiocyanogen and TiO₂, and leads to high N₂/N₂O ratios. The reduction of NO in the presence of Cu-containing paracyanogen or Cu is not a photocatalytic reaction, and yields relatively low N₂/N₂O ratios.