Chemistry of Diazocarbonyl Compounds: XVIII. Synthesis and Spectral Parameters of 1,3-Dialkyl- 3-hydroxy-2-diazoketones

Reduction of the carbonyl groups in cyclic and acyclic 2-diazo-1,3-diketones with sodium tetrahydridoborate in aqueous–alcoholic medium, followed by hydrolysis of the reaction mixture over wet silica gel and chromatographic purification on neutral aluminum oxide, afforded 1,3-dialkyl-3-hydroxy-2-diazoketones in 58–87% yield. Bulky substituents at the carbonyl group considerably reduce the efficiency of the process, and the reduction of cis- and trans-4,6-di-tert-butyl-2-diazocyclohexane-1,3-diones is characterized by low stereoselectivity (de 40–49%). In the IR spectra of 3-hydroxy-2-diazocyclohexanes, absorption bands corresponding to stretching vibrations of free axial hydroxy groups are located at higher frequencies (by 20-45 cm^-1) than those belonging to equatorial hydroxy groups. These parameters may be useful for conformational analysis of cyclic hydroxy diazo ketones. Stabilization of the E conformation of acyclic hydroxy diazo ketones via intramolecular hydrogen bonding is likely to occur only in nonpolar solvents (CCl₄, cyclohexane).     

Gas phase ionization of 1,3-propanedial tautomeric forms: A theoretical study

Two stable 1,3-propanedial tautomers and three their anions have been studied theoretically at MP2 and DFT levels of theory. The energies, structural parameters, ionization potentials, and vibration frequencies have been calculated at the two theoretical levels in order to compare the accuracy of the methods used. The ionization potential of the end form of 1,3-propanedial enol form was estimated to be 752 kJ mol^?1; the first and second potentials of the diketo form of 1,3-propanedial are 661 and 1239 kJ mol^?1, respectively.     

Benzo-1,2,3-oxadiazole and 6-Diazocyclohexa-2,4-dienone: Structures and Relative Energies of Molecules

Structural parameters, IR spectra, ionization potentials, relative energies, isomerization barriers, and solvation energies have been calculated for the aromatic benzo-1,2,3-oxadiazole (prevalent tautomer in the gas phase) and zwitterionic 6-diazocyclohexa-2,4-dienone (prevalent tautomer in a polar solvent) molecules. Similar calculations indicated that unsubstituted 1,2,3-oxadiazole is unstable in all solvents.Original Russian Text Copyright © 2004 by S. G. Semenov and Yu. F. Sigolaev__________Translated from Zhurnal Strukturnoi Khimii, Vol. 45, No. 6, pp. 1128–1131, November–December, 2004.     

Prins-Reaktionen mit Arylaldehyden, 5. Mitt.: Zur Umsetzung mit 2-Buten und mit Cyclohexen

By reaction of 2-[(1RS, 2RS)-2-hydroxy-1-methyl-propyl]-2-phenyl-1,3-dithiane (1 a) withcis-2-butene oxide, subsequent reduction and acetalizationc-4,t-5-dimethyl-r-2,c-6-diphenyl-1,3-dioxane (3 a) andt-4,c-5-dimethyl-r-2,c-6-diphenyl-1,3-dioxane (3 b) were synthesized as model compounds. For the same purpose by aldol reaction of cyclohexanone and reduction (1RS, 2SR)-2[(RS)-hydroxy-(4-methoxyphenyl)methyl]cyclohexanol (7 a), (1RS, 2RS)-2[(SR)-hydroxy-(4-methoxyphenyl)methyl]cyclohexanol (8 a), and (1RS, 2RS)-2[(RS)-hydroxy-(4-nitrophenyl)methyl]cyclohexanol (8 b) and by acetalization (2 , 4 , 4 a, 8 a)-2,4-bis(4-methoxyphenyl)hexahydro-4H-1,3-benzodioxin (9 a) and (2 , 4 , 4 a, 8 a)-2,4-bis(4-nitrophenyl)hexahydro-4H-1,3-benzodioxin (10 b) were obtained. FromPrins reactions, starting with 2-butene3 a,c-4,c-5-dimethyl-r-2,c-6-diphenyl-1,3-dioxane (3 c),r-4,t-5-dimethyl-c-6-phenyl-1,3,2-dioxathiane-2,2-dioxide (4), and (2Z, 4E)-1,5-diphenyl-4-methyl-2,4-pentadien-1-on (5), and starting with cyclohexene (E)-3-(4-methoxybenzylidene)cyclohexenyl-4-methoxyphenyl ketone (11) have been isolated in low yields.

4. Mitt.:Griengl, H., Nowak, P., Mh. Chem.109, 11 (1978).     

Electrochemical oxidative methoxylation of 4H-imidazole 1,3-dioxides to give α-methoxy substituted nitroxyl radicals

Electrochemical methoxylation of substituted 4H-imidazole 1,3-dioxides has been carried out for the first time. Nitroxyl radicals of the 2- and 3-imidazoline series with methoxy groups at the -carbon atom of the radical site were synthesized. The yields and ratios of the electrochemical methoxylation products are close to those observed in the chemical methoxylation carried out with PbO₂ and MnO₂ as oxidants.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp.469–471, March, 1994.     

Electronic structure,spectra, and thermodynamical functions of molybdenum pentachloride

The SCF-X -SW method in non-relativistic and quasi-relativistic versions has been used to calculate the electronic structure, ionization potentials, energies and oscillator strengths of the optical transitions in MoCl₅. The electronic absorption spectrum of the gaseous MoCl₅ has been measured. The interpretation of the photoelectron and optical spectra of MoCl₅ is given. Spinpolarization effects and relativistic corrections are discussed. The thermodynamical functions of MoCl₅ (gas) are calculated.     

Studies in the field of 2, 1, 3-Thiadiazole and 2,1, 3-Selenadiazole

Benzo-2, 1, 3-thiadiazole (I) undergoes chloromethylation with dichlorodimethyl ether in the presence of anhydrous aluminum chloride with the predominant formation of 4, 7-di(chloromethyl)benzo-2, 1, 3-thiadiazole (II). Bases and pseudobases (paraformaldehyde, hexamethylenetetramine, dimethylformamide) exert an inhibiting influence on this reaction. In the presence of these substances, a mixture of compound II and 4-(chloromethyl)benzo-2, 1, 3-thiadiazole (III) is formed, or else no reaction takes place. The structures of compounds II and III has been shown by their reductive decomposition to o-diamines described in the literature. The high reactivity of the chlorine in the chloromethyl group has enabled various new derivatives of benzo-2, 1, 3-thiadiazole to be obtained by its replacement with hydroxy, thiocyanato, di(-hydroxyethyl)amino, di(-chloroethyl)amino, formyl, and carboxy groups.For communication XLVIII, see [11].     

High levelab initio stabilization energies of benzene

Summary G2 theory is shown to be reliable for calculating isodesmic and homodesmotic stabilization energies (ISE and HSE, respectively) of benzene. G2 calculations give HSE and ISE values of 92.5 and 269.1 kJ mol^–1 (298 K), respectively. These agree well with the experimental HSE and ISE values of 90.5±7.2 and 268.7±6.3 kJ mol^–1, respectively. We conclude that basis set superposition error corrections to the enthalpies of the homodesmotic or isodesmic reactions are not necessary in calculations of the stabilization energies of benzene using G2 theory. The calculated values of the enthalpies of formation of such molecules containing multiple bonds such as benzene ands-trans 1,3-butadiene, which are found from the enthalpies of isodesmic and homodesmotic reactions rather than of atomization reactions, demonstrate good performance of G2 theory. Estimates of theH _f ^o value for benzene from the G2 calculated enthalpies of homodesmotic reaction (2) and isodesmic reaction (3) are 80.9 and 82.5 kJ mol^–1 (298 K), respectively. These are very close to the experimentalH _f ^o value of 82.9±0.3 kJ mol^–1. TheH _f ^o value ofs-trans 1,3-butadiene calculated using the G2 enthalpy of isodesmic reaction (4) is 110.5 kJ mol^–1 and is in excellent agreement with the experimentalH _f ^o value of 110.0±1.1 kJ mol^–1.     

Reaction of dialkyl 2-aryl-4-hydroxy-4-methyl-6-oxocyclohexane-1,3-dicarboxylates with aliphatic amines

Benzylamine, phenethylamine, and homoveratrylamine reacted with dialkyl 2-aryl-4-hydroxy-4-methyl-6-oxocyclohexane-1,3-dicarboxylates at the endocyclic carbonyl group with conservation of the enolic hydroxy group to give dialkyl 4-alkylamino-2-aryl-6-hydroxy-6-methylcyclohex-3-ene-1,3-dicarboxylates. The reaction of dimethyl 4-hydroxy-4-methyl-6-oxo-2-phenylcyclohexane-1,3-dicarboxylate with tryptamine was accompanied by dehydration with formation of dimethyl 4-[2-(1H-indol-3-yl)ethylamino]-6-methyl-2-phenylcyclohexa-3,5-diene-1,3-dicarboxylate, presumably due to basic properties of the indole nitrogen atom.     

13C NMR study on the methoxy carbon chemical shifts in chloro-substituted anisoles and guaiacols

The ¹³C NMR chemical shifts of methoxy carbons in chlorinated anisoles and guaiacols have been measured for acetone-d₆ solutions. Multiple linear regression analysis, and also ‘simple sum rule’ calculations, have been used to estimate the effects of the chlorine atoms (the position and degree of substitution) on the chemical shifts. The most important effects have shown to be due to the chlorine atoms adjacent to the methoxy and hydroxy substituents. For chlorinated guaiacols, the greatest effect is due to the chlorine atom adjacent to the methoxy group. For chlorinated anisoles, the substituents adjacent to the methoxy group (2,6-disubstitution) cause large effects. For both groups of compounds, the chemical shifts are also greatly influenced by the number of chlorine substituents. Using the three most important independent variables, the average differences between the observed and calculated chemical shifts are ca 0.2 ppm for anisoles and 0.1 ppm for guaiacols. For chloroguaiacols, the corresponding difference was only 0.1 ppm when calculations were performed using single substituent effects.     

19F NMR study ofcis- andtrans- effects of substituted triphenylphosphine ligands intrans-(4-fluorophenyl)triarylphosphine-tri(4-fluorophenyl)phosphineplatinum 4-fluorothiophenoxides

A number of compounds of the type oftrans-4-FC₆H₄Pt(PAr₃)₂SC₆H₄F-4, where Ar is a substituted phenyl group, have been prepared starting from the corresponding chlorides. By exchange reactions oftrans-4-FC₆H₄Pt[P(C₆H₄F-4)₃]₂SC₆H₄F-4 with the above-mentioned compounds or Ar₃P,trans-4-FC₆H₄Pt[P(C₆H₄F-4)₃][PAr₃]SC₆H₄F-4 have been generated in solution. For the latter compounds, the effect of Ar₃P oncis- andtrans-ligands has been studied by the¹⁹F NMR technique. It has been shown that thecis- andtrans-effects of Ar₃P run parallel and are well described by pK _a values and ionization potentials of the unshared electron pair in Ar₃P, as well as by ⁰ constants of the aryl groups.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1359–1363, July. 1995.     

Regioselective and Regiospecific Cycloaddition of Acetylenes to 2,4,6-Triazidopyridine

The cycloaddition of tert-butylacetylene to 2,4,6-triazido-3,5-dicyanopyridine and 2,4,6-triazido-3-chloro-5-cyanopyridine occurs regioselectively and regiospecifically at the azide group in position 4 of the pyridine ring leading to the formation of the corresponding 4-(4'-tert-butyl-1H-1,2,3-triazolyl)pyridines as the sole products. Analogous reactions with the less sterically hindered n-butylacetylene are characterized by less regiospecificity and give a mixture of the isomeric 4'- and 5'-n-butyl-substituted triazoles at ratios of 96 : 4 and 91 : 9 respectively for the two different triazides. The interaction energies of the pyridine - and -azide groups with the acetylene molecules, and the energies of the transition states for these reactions have been calculated by the PM3 method. It was established that the high reactivity of the -azide group of the triazidopyridines in relation to the! ace tylenes is caused by the anomalously low distribution of bonding orbital density on these groups, leading to substantially lower activation energies in 1,3-dipolar cycloaddition reactions.     

Scopolamine and atropineN-methyl diastereomer stability.Ab initio calculations onO-formylscopine andO-formyltropine model compounds

Ab initio geometry optimizations at the RHF-21G basis set level were calculated forequatorial andaxial N-methyl diastereomers ofO-formyltropine andO-formylscopine esters and other model compounds. These optimized geometries were then utilized as input for single-point energy calculations using the higher level RHF/6-31G^* basis set to afford a more precise estimation of the total energies and atomic charges. Ethano bridge pinching of theN-protonated tropanyl piperidine moiety pushes the smalleraxial N-proton closer toward the neighboring twoaxial C-H bonds compared with the analogous case for a bulkyaxial N-methyl. Increasedcis 1,3-diaxial interactions in theaxial N-methyl diastereomer destabilize this epimer in favor of theequatorial N-methyl counterpart [e.g., 2.121 kcal/mol lower energy for theequatorial N-methylO-formyltropineN-protonated diastereomer (12) than for theaxial epimer (13)]. Lower pyramidality at nitrogen in the free base maintains the relative stability of theequatorial N-methyl free base diastereomer (14) (1.120 kcal/mol more stable than theaxial free base15). A nonprotonated carbon atom at the apex of a three-membered ring fused to the 6,7-positions of theO-formyltropine skeleton results in severe transannular nonbonding steric interactions involving the neighboringequatorial N-methyl group inN-protonated16 (3.335 kcal/mol less stable than theaxial N-methyl epimer17, where these transannular interactions are reduced due to the smallerequatorial N-H proton). Oxygen atom occupation of the apex of a similar fused three-membered ring retains the same severe transannular nonbonding steric interactions involving the neighboringequatorial N-methyl group inN-protonated18. These transannular interactions now become electrostatically attractive in theN-protonatedaxial N-methyl epimer19 (2.031 kcal/mol more stable than theequatorial epimer). Reduced pyramidality at nitrogen in theO-formylscopine free base reduces the repulsive transannular interaction with the neighboringequatorial N-methyl group compared to that in theN-protonated form. Lowered pyramidality also reduces thecis-1,3-diaxial interactions in theaxial N-methyl epimer, but the nitrogen lone pair is pushed close to the transannular oxygen lone pair as a result (theequatorial N-methyl free base20 is 3.870 kcal/mol more stable than theaxial epimer21). Theseab initio-calculated models ofO-formyltropines andO-formylscopineN-methyl diastereomeric protonated cations and free bases provide stereochemical insight into the relative stabilities of solution-state atropine and scopolamineN-methyl species previously observed by NMR spectroscopic methods.     

Potential Functions for Internal Rotation about the Csp2-O Bond and Intramolecular Interactions in p-RC6H4OCH3 Compounds

Potential functions for internal rotation about the Csp²ÄO bond in p-RC₆H₄OCH₃ compounds (R = NH₂, OCH₃, CH₃, H, F, Cl, CN, NO₂) were determined by nonempirical quantum-chemical calculations in the HF/6-31G* and MP2/6-31G* approximations with account taken of correlation energy for all electrons. The molecular conformation is planar. The height of the rotation barrier changes, depending on the electronic effect of para-substituent. Electron-donor substituents reduce while electron-acceptor substituents enhance the stability of the planar conformation. Using the natural bond orbital (NBO) approach, the nature of lone electron pairs on the methoxy oxygen atom was analyzed, and the energies for their resonance interaction with the antibonding aromatic * orbitals were determined. The effect of para-substituent on the electron density distribution over the methoxy group and on the Koopmans first ionization potentials was estimated. Geometric parameters of the molecules under study are given.     

Thoeretical study of the tautomerism of nucleotide bases in the gas phase and in aqueous media

The relative stabilities of the tautomers of nucleotide bases in the gas phase and in aqueous media were estimated by the self-consistent field (SCF) MO method within the-electron approximation. It is shown that the solvation energy, which depends substantially on the order of the tautomers with respect to their energies, must be taken into account for the accurate evaluation of the most stable tautomeric structure. The probabilities of spontaneous mutations in the gas phase and in aqueous media were estimated. The ionization potentials and electron affinities of the normal and rare tautomeric structures were calculated.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 1, pp. 94–99, January, 1978.     

Synthesen von Heterocyclen, 68. Mitt.: ÜberMannich-Basen heterocyclischer β-Dicarbonylverbindungen

Zusammenfassung Durch Variation der Versuchsbedingungen konntenMannich-Basen vom 6-Methyl-2,4-pyronon, 2-Äthoxy-4-hydroxy-[1,3-thiazinon-(6)] und von verschiedenen 2-Phenyl-4-hydroxy-[1,3-thiazinonen-(6)] sowie vom 4-Hydroxy-5,6,7,8-tetrahydrocumarin, Malonyl--aminopyridin und -Oxo--hydroxy-julolin hergestellt werden. Auch Barbitursäure und Thiobarbitursäure lassen sich unter gewissen Bedingungen aminoalkylieren.

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Mannich bases have been obtained from 6-methyl-2,4-pyronon, 2-ethoxy-4-hydroxy-1,3-thiazinon-(6), 2-phenyl-4-hydroxy-1,3-thiazinones-(6), 4-hydroxy-5,6,7,8-tetrahydrocoumarin, malonyl--aminopyridin and -oxo--hydroxy-julolin by appropriate variation of the reaction conditions. Also barbituric acid and thiobarbituric acid have been aminoalkylated under certain conditions.

     

An ab initio CI study of the ground and excited states of p-quinodimethane

Configuration interaction (CI) studies of the ground, electronically excited singlet and triplet states and of the ionized states (cations) are reported for p- quinodimethane (p-xylylene). The calculated ionization potentials are compared with the experimental photoelectron spectrum for the low-energy ionization region. The two high-energy low-intensity flanks of the second and third band observed in the photoelectron spectrum are assigned to be due to the two non-Koopmans' cation states, ascribing to shake-up ionizations.The calculated singlet-singlet and singlet-triplet excitation energies are compared with previous semiempirical MO results and experimental data.     

Synthesis and properties of functional derivatives ofN′-phosphoryl- andN′-phosphonoyldiazeneN-oxides; molecular structure ofN-(2,2-dimethyl-5-nitro-1,3-dioxan-5-yl)-N′-[methoxy(phenyl)phosphoryl]diazeneN-oxide

Methods for the synthesis of polyfunctionalN-phosphoryl- andN-phosphonoyldiazeneN-oxides containing hydroxyl, acetoxyl, and nitrate groups, and dibromoallyl and dibromopropyl fragments have been developed. The molecular structure ofN-(2,2-dimethyl-5-nitro-1,3-dioxan-5-yl)-N-[methoxy(phenyl)phosphoryl)diazeneN-oxide was established by X-ray structural analysis.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1284–1289, July, 1994.     

Electron interaction in molecules

An idea of electron interaction in molecule has been applied to the SCF MO calculations of theπ-electronic structure of some complex aromatic hydrocarbons and their derivatives. The theoretical results for singlet and triplet transition energies, first ionization potentials and bond lengths agree fairly well with the experimental data. A correlation equation between the valence state ionization potential and the one center electron repulsion integral has been proposed. It has been shown that the electron repulsion in molecule is considerably smaller than in free atom. The present calculation shows that we can treat sulphur as a normal heteroatom analogous to oxygen and nitrogen.     

Calculation of some atomic properties by gradient corrected density functional method

Using thePerdew andPerdew-Wang Yue gradient expansion functionals the total electronic binding energies, the ionization potentials and the KL transitin energies are calculated for the atoms of elements from Be to Cu, and the 3d–4s transition energies are determined for the third row elements. There is a general improvement with respect to the results found without gradient corrections. However the asymptotic behavior of the potential does not changes.