Stepwise charge transfer complexation of some pyrimidines with sigma-acceptor iodine involving a new unconventional acceptor

Interactions of some pyrimidine derivatives, 4-amino-2,6-dimethylpyrimidine, kyanmethin, (4AP), 2-amino-4,6-dimethylpyrimidine (2AP), 2-aminopyrimidine (AP), 2-amino-4-methylpyrimidine (AMP), 2-amino-4-methoxy-6-methylpyrimidine (AMMP), and 4-amino-5-chloro-2,6-dimethylpyrimidine (ACDP) as electron donors, with iodine (I(2)), as a typical sigma-electron acceptor, have been studied. Electronic absorption spectra of these interactions in several organic solvents of different polarities have performed instant appearance of clear charge transfer (CT) bands. Formation constants (KCT), molar absorption coefficients (epsilonCT) and thermodynamic properties, DeltaH, DeltaS, and DeltaG, of these interactions have been determined and discussed. Electronic absorption spectra of the solutions of the synthesized pyrimidines-iodine, P-I2, CT complexes have shown the characteristic bands of the triiodide ion, I3*. UV/vis spectral tracking of these interactions have shown that by lapse of time the first formed CT complex, P-I2, is transformed to the corresponding triiodide complex, P(+)I.I3*, then, the later interacts as a new unconventional acceptor and it forms a CT complex of the form (P).(P+I.I3*). Elemental analyses of these solid complexes have indicated the stoichiometric ratio 2:2, or formally 1:1, P:I2.     

A structural and magnetic study of organolanthanide(III) amides

The syntheses, structures and magnetic properties of the series of dimeric organolanthanide(III) amides [Cp2Ln{2-NH-4,6-Me2pm}]2 [Ln = Nd (1), Gd (2), Dy (3), Yb (4) and pm = pyrimidine], which are formed from the deprotonation of 2-amino-4,6-dimethylpyrimidine by the corresponding lanthanide tris-cyclopentadienide, are reported. The synthesis and structure of [{Cp2Yb(2-NH-4-MeO-6-MeOpm)(2)(mu3-O)(YbCp)] (5), formed in a similar deprotonation reaction but in the presence of adventitious water, is also reported.     

Reactions of triacetylmethane with monosubstituted hydrazines and amidine analogues. Syntheses of 4-acetyl-3,5-dimethylpyrazole amidinohydrazone and 1,3,5-triazine derivatives

Triacetylmethane ( 1 ) reacts with amidinohydrazines in acidic medium to afford 4-acetyl-3,5-dimethylpyrazole amidinohydrazone derivatives 2,4 . However, a similar reaction of 1 with thiosemicarbazide or semicarbazide led mainly to 3,5-dimethylpyrazole ( 6 ). The great propensity of 1 to hydrolysis accounts for this last transformation, as well as for the fact that with guanidine it led to 2-amino-4,6-dimethylpyrimidine ( 10 ) and with S-methylisothiourea it provided the unexpected 2-amino-4-methyl-6-methylthio-1,3,5-triazine ( 11 ).     

Cyclic condensations of 2-amino-1,3,4-thiadiazole with 1,3-dicarbonyl compounds

The reactions of 2-amino-1,3,4-thiadiazole with 1,3-dicarbonyl compounds are described. 2,4-Pentanedione gave 2-thiocyanato-4,6-dimethylpyrimidine while diethylmalonate and ethyl acetoacetate yielded 5-hydroxy-7H-1,3,4-thiadiazolo[3,2-a]pyrimidin-7-one and 7-methyl-5H-1,3,4-thiadiazolo[3,2-a]pyrimidin-5-one, respectively. The structure of the latter compound was confirmed by a synthesis of the alternative isomeric structure (5-methyl-7H-1,3,4-thiadiazolo[3,2-a]pyrirnidin-7-one) from 2-amino-1,3,4-thiadiazole and α-bromocrotonic acid.     

1-(4-甲氧基)苯甲酰基-3-(4,6-二甲基嘧啶-2-氨基)硫脲的晶体结构、 理论计算及生物活性

2-氨基-4,6-二甲基嘧啶与硫氰酸钾、4-甲氧基苯甲酰氯在乙酸乙酯中反应, 合成了1-(4-甲氧基)苯甲酰基-3-(4,6-二甲基嘧啶-2-氨基)硫脲, 并用X射线单晶衍射法测定其晶体结构, 晶体属单斜晶系, 空间群为P21/n, 晶胞参数为: a＝1.0134(4) nm, b＝1.3172(5) nm, c＝1.0988(4) nm, β＝91.671(8)°, V＝1.4661(9) nm3, Dc＝1.433 g/cm3, μ＝0.234 mm－1, F(000)＝664, Z＝4, R1＝0.0571, wR2＝0.1328. 运用Gaussian 03程序, 对标题化合物进行了HF/6-31＋g(d)和B3LYP/6-31＋g(d)水平的几何全优化和频率计算, 并对其成键情况及自然键轨道(NBO)进行了分析. 初步实验证明该化合物具有良好的生物活性.     

5,7-Dimethyl-3-phenylfurazano- and -furoxano[5,4-a]pyrimidinium perchlorates: New types of condensed systems

5,7-Dimethyl-3-phenylfuroxano[5,4-a]pyrimidiniumperchlorate (II) was obtained by the reaction of 4-amino-3-phenylfuroxan with acetylacetone in the presence of HClO₄. The structures of II and its furazan analog I were proved by x-ray diffraction analysis, and their ¹³C NMR spectra were studied. The cations of I and II (which contain a conjugated condensed system with delocalization of the positive charge) and their monocyclic analogs — phenylfarazan, 3-phenylfuroxan, and 4,6-dimethylpyrimidine — were subjected to quantum-chemical calculation by the CNDO/2 method.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 233–238, February, 1992.     

An improvement in the synthesis of ethyl pyrimidinecarbamates

It is demonstrated that N-(ethoxycarbony])pyridinium chloride ( 3 ) is the reactive agent in the synthesis of 4-ethoxycarbonylamino-2,6-dimethylpyrimidine ( 1 ). A good yield (80%) of 1 may be obtained by the condensation of 3 with excess 4-amino-2,6-dimethylpyrimidine using pyridine or dimethylformamide as the solvent. A method allowing for the preparation of 4-ethoxycarbonylamino-x-hydroxypyrimidines via the same process is offered.     

Photoinduced amino-imino tautomerization reaction in 2-aminopyrimidine and its methyl derivatives with acetic acid

The electronic absorption and fluorescence spectra of 2-aminopyrimidine (2APM), 2-amino-4-methylpyrimidine (2A4MPM), and 2-amino-4,6-dimethylpyrimidine (2ADMPM) with acetic acid (AcOH) were measured in isooctane (2,2,4-trimethylpentane) at room temperature. From the absorption spectra, a hydrogen-bonded complex formation of the 2APM/AcOH, 2A4MPM/AcOH, and 2ADMPM/AcOH systems was recognized in isooctane. The enthalpy changes (-DeltaH) for the complex formation were estimated to be ca. 41.2-45.1 kJ mol-1 and increased in proportion to the numbers of the methyl group introduced into the 2APM. The -DeltaH values refer to the formation of the hydrogen-bonded 1:1 complex between the ring nitrogen atom and NH2 group of the aminopyrimidine and the OH and CO groups of AcOH, respectively. In the 2A4MPM/AcOH double hydrogen-bonded complex the OH group of AcOH is thought to be linked to the ring nitrogen at the 1-postion of 2A4MPM. The fluorescence spectral results indicate that the double proton transfer reaction takes place during the excited state, and gives rise to an imino-tautomer vibration emission, from analogy with the fluorescences of 1-methyl-2(1H)-pyrimidinimine (MPMI), 1,4-dimethyl-2(1H)-pyrimidinimine (DMPMI), and 1,4,6-trimethyl-2(1H)-pyrimidinimine (TMPMI). The fluorescence quantum yields of the imino-tautomers also increased in proportion to the numbers of the methyl group introduced into the 2APM.     

Etude de la fragmentation par impact électronique en ions positifs et négatifs de dérivés nitrés de l'amino-2-benzothiazole

Study of Positive and Negative Ions Electron Impact Fragmentation of 2-Amino-benzothiazole Nitro Derivatives The positive and negative ions mass spectra of 2-amino-4,6-dinitrobenzothiazole ( 1 ), 2-amino-4-nitrobenzothiazole ( 2 ), 2-amino-6-nitrobenzothiazole ( 3 ) are reported and discussed. These compounds give an intense molecular ion and show interesting fragmentations in both positive and negative ions spectra. Specific ¹⁵N-labelling was used in order to confirm the fragmentation patterns.     

Functionally substituted azines. 1. Synthesis and reactions of 2-(N-cyano-N-carbethoxmethylamino)-4,6-dimethylpyrimidine

Treatment of 2-(N-potassium-N-cyanamino)-4,6-dimethylpyrimidine with ethyliodoacetate produces 2-(N-cyano-N-carbethoxymethylamino)-4,6-dimethylpyrimidine. Alkaline hydrolysis of the last gives 2-(3-potassium-2,4-dioxoimidazolidinyl-1)-4,6-dimethylpyrimidine. Ammonolysis and hydrazinolysis give imino- or amino-imidazolidinylpyrimidine, respectively.Armenian Agricultural Institute, Erevan 375009. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1239–1241, September, 1994. Original article submitted August 9, 1994.     

Electronic and vibrational spectral studies of substituted mercaptopyrimidines

The vibrational spectra (i.r., far i.r. and Raman) of 4,6-dimethyl-2-mercaptopyrimidine and 4,6-dihydroxy-2-methylmercaptopyrimidine have been reported along with their assignments. Hydrogen bonding and tautomeric behaviour are discussed. Electronic spectra in various solvents at different pH values are recorded. The effect of a change of solvent on the electronic transitions of both compounds is explained along with the bathochromic and hypsochromic shifts observed when the neutral form of the compound is changed to the anionic or cationic form.     

Diorganyl ditellurides with intramolecular coordination bonds: synthesis and structure of bis(4,6-dimethylpyrimidin-2-yl) ditelluride

A reaction of 2-chloro-4,6-dimethylpyrimidine with sodium ditelluride in DMF afforded bis(4,6-dimethylpyrimidin-2-yl) ditelluride, a new representative of dihetaryl ditellurides. An X-ray diffraction study revealed an unusual planar trans-conformation of this compound, which is stabilized by both intramolecular attractive non-valent Te...N interactions (3.082(2) Å) and π-stacking of the aromatic heterocycles (the centers of the pyrimidine rings are disposed at 3.421(3) ). The energy parameters of the factors that make the molecular structure flattened were estimated by quantum chemical DFT calculations.     

Synthesis and Crystal Structure of 4-（4,6-dimethoxyl -pyrimidin-2-yl）-3-thiourea Carboxylic Acid Methyl Ester

1 INTRODUCTION Pyrimidinyl thioureas have been studied for many years because of their broad antibiosis and sterilibza- tion properties. Recent years’ study shows that pyri- midinyl thioureas not only can be used to kill insects and adjust plant growth, but also have anti-viral ac- tivities[1, 2]. From our early quantum study on these compounds, we find that they have several active cen- ters and can form polyligand complexes with metals easily[3]. These complexes are widely used as ant…     

Experimental and quantum chemical studies of the electronic absorption spectra of pyrimidine derivatives

The electronic absorption spectra of different pyrimidine derivatives have been measured experimentally and calculated theoretically by the PPP and CNDO/S methods. These pyrimidine derivatives are: 4,6-dichloro-pyrimidine (I), 4,6-dichloro, 5-amino-pyrimidine (II), 2,4,6-trichloro-pyrimidine (III), 4,6-dihxdroxy-pyrimidine (IV), 4,6-dihxdroxy-5-nitro-pyrimidine (V), 2,4-diamino-pyrimidine (VI), 2,4-diamino-6-hydroxy-pyrimidine (VII), 2,4-dihydroxy-5-carboxy-pyrimidine (VIII), 2,4-dimethyl-6-hydroxy-pyrimidine (IX), 5-nitro-uracil (X), and orotic acid (XI). The observed electronic spectral shifts are quantitatively analyzed in relation to different solute–solvent interaction mechanisms. The effects of solvent polarity and hydrogen bonding on the spectra are discussed in the light of theoretical predictions. This comparative analysis provides a reasonable picture of the solvent effects on the absorption spectral properties of pyrimidine nucleobases.     

5-(4,6-Diphenyl-2-pyrimidinyl)-1,3,4-oxadiazole-2-thione with Some C-Electrophiles and N-Nucleophiles

5-(4,6-Diphenyl-2-pyrimidinyl)-1,3,4-oxadiazole-2-thione reacted with haloalkanes or their derivatives containing side chain oxo group to give S-alkylated compounds. Aminomethylation and acylation of the thione yielded N₍₃₎-derivatives. Treatment of the title compound with hydrazine hydrate in butanol resulted in 4-amino-5-(4,6-diphenyl-2-pyrimidinyl)-1,2,4-triazole-3-thione via a recyclization reaction. Reaction of the title compound with hydrazine hydrate or phenylhydrazine in dioxane led to formation of the corresponding thiocarbohydrazides. The latter in the presence of a base were cyclized to 4-amino-1,2,4-triazole-3-thiones.     

Tautomeric equilibria of 2(4)-monooxopyrimidines in the gas phase,in low-temperature matrices and in solution

IR absorption spectra, including the NH, OH and CO stretching regions, have been recorded for 4-oxo-6-methyl- and 2-oxo-4,6-dimethyl pyrimidines and several related derivatives, in the gas phase, in low-temperature inert matrices, and in several liquid solvents.All the 4-oxopyrimidines in the gas phase, and 4-oxo-6-methylpyrimidine in low-temperature matrices, exhibit comparable populations of the keto and enol forms. By contrast the 2-oxopyrimidines are predominantly in the enol forms. Both classes of com pounds are predominantly in the keto form in liquid solvent systems. The tautomeric equilibrium constant (K_T) in the vapour phase for 4-oxo-2,6-dimethylpyrimidine is about 2, and for the other 4-oxopyrimidines is about 1. For 4-oxo-6-methylpyrimidine, the equilibrium constant in inert matrices varies slightly with the activity of the matrix gas, with the keto tautomer favoured in the more active matrix. From the temperature-dependence of K_T the free energy difference between the two tautomeric forms of 4-oxo-6-methylpyrimidine in the vapour phase has been calculated. Heats of vaporization have also been calculated for the various compounds and related to their abilities to associate by hydrogen bonding in the condensed phase.The UV absorption spectra of some of the foregoing have also been recorded in the gas phase, but these were of only limited value in studies of tautomeric equilibria, as connpared to the IR spectra.     

Synthesis and Antimicrobial Activity of Methyl (2 Z )-4-Aryl-2-{4-[(4,6-dimethylpyrimidin-2-yl)sulfamoyl]phenylamino}-4-oxobut-2-enoates and Their Silver Salts

A series of new methyl (2Z)-4-aryl-2-{4-[(4,6-dimethylpyrimidin-2-yl)-sulfamoyl]phenylamino}-4-oxobut-2-enoates was synthesized by the reaction of methyl esters of aroylpyruvic acids with 2-(4-aminobenzenesulfamido)-4,6-dimethylpyrimidine in a mixture of acetic acid–ethanol (1 : 1). The obtained 4-oxobut-2-enoates reacted with silver nitrate in ethanol–DMF (2 : 1) to form their silver salts. The antimicrobial activity of the compounds was studied.     

Molecular and Crystal Structure of 4,6-Dimethyl-2-(phenylhydrazino)pyrimidine and Its Alkylation and Protonation Products

It was established by X-ray crystallographic analysis that 4,6-dimethyl-2-(phenylhydrazino)pyrimidine forms 2-(2-n-butyl-2-phenylhydrazino)-4,6-dimethylpyrimidine during alkylation with n-butyl bromide and 4,6-dimethyl-2-(phenylhydrazino)-1(H)-pyrimidinium nitrate during protonation with nitric acid. The structure of the molecules and the system of intermolecular hydrogen bonds in the crystals of the compounds are discussed.     

Investigations on crystal structure of a novel 3-((4,6-dimethylpyrimidin-2-yl)amino)isobenzofuran-1(3H)-one,and related theoretical studies

In this report, 3-((4,6-dimethylpyrimidin-2-yl)amino)isobenzofuran-1(3H)-one have been synthesized via reaction between phthalaldehydic acid and 2-amino-4,6-dimethylpyrimidine in 90% yields and characterized by Infrared (IR), Nuclear Magnetic Resonance (NMR), Ultraviolet–visible (UV–Vis), X-ray single crystal diffraction techniques. The single-crystal X-ray analysis shows that the title compound crystallizes in the triclinic space group P-1 with unit-cell parameters a = 7.9351(4) Å, b = 11.1687(6) Å, c = 16.1281(9) Å, α = 73.713(5)°, β = 80.362(5)°, γ = 72.882(4)° and Z = 4. A theoretical study with hybrid functional B3LYP 6-311G (d, p) basis set have been used in calculations. The structural and electronic properties have been detailed. The title compound was screened for its antioxidant activity by (1,1-diphenyl-2-picryl hydrazyl) free radical scavenging (DPPH), Ferric ion reducing antioxidant power (FRAP), total phenolic contents (TP) assays and its ferrous ions chelating property. Electronic absorption titration, thermal denaturation measurement and viscosity techniques were used to determine the interaction between double stranded DNA (dsDNA) and compound 1. In three techniques, the mode of binding of compound 1 to dsDNA is minor groove. The UV–Vis measurement results allowed the calculation of the binding constant showing the binding strength of compound 1 to dsDNA was calculated as 8.13 × 10⁴ ± 0.07 L mol⁻¹. Moreover, the molecular docking calculations have been performed to investigate the compound–DNA interactions, computationally. In molecular docking calculations, it was observed that for the title compound, the lowest energy docking pose takes place in the minor groove of DNA and in addition to minor groove binding, interactions between the compound and the consecutive base pairs of DNA which may cause a partial intercalation were also observed. Results showed that title compound – DNA complex is stabilized by several hydrogen bonds, and Pi-alkyl interactions also take part in the stabilization of the complex. Binding affinities of the lowest energy docking pose of the title compound was found to be −8.3 kcal/mol.     

Ring transformations of 4H-pyrans. Pyridines from 2-amino-4H-pyrans

Ring transformations of 4H-pyrans into pyridines are reported. Treatment of 2-amino-4,6-diaryl-3,5-dicyano-4H-pyrans (I) with nitrosylsulfuric acid brings about their transformation into 3,5-dicyano-4,6-diaryl-2-pyridones (VI) which can also be obtained from α-benzoylcinnamonitriles (IX) and cyanoacetamide. Similarly, 2-amino-4,6-diaryl-5-carbethoxy-3-cyano-4H-pyrans (II) lead to 4,6-diaryl-5-carbethoxy-3-cyano-2-pyridones (VII). Treatment of both series of pyrans with sulfuric acid results in the formation of the corresponding 3,4-dihydro-2-pyridones (IV and V). Reaction of pyrans II with ammonium acetate in acetic acid yields 2-amino-4,6-diaryl-5-carbethoxy-3-cyanopyridines (XII). Pyrans I undergo an entirely different type of reaction upon treatment with this reagent leading to 2,4,6-triaryl-3,5-dicyano-1,4-dihydropyridines (XV).