Eremophilane esters of Robinsonecio gerberifolius and their rearranged products. Study of the coupling constants (2)J(H, H), (3)J(H, H) and (4)J(H, H)

In the course of the basic hydrolysis of four eremophilane esters isolated from Robinsonecio gerberifolius, some rearrangements, eliminations, and additions occurred. Five compounds were obtained, three of them not previously described. Additionally, a new sesquiterpene was produced by autooxidation of compound 1. The (1)H and (13)C NMR spectra of these compounds were completely assigned by utilization of HMQC, HMBC, COSY, DEPT, and NOESY techniques. The long-range coupling constants of the peroxide 10 are reported, and all its coupling constants (2)J(H, H), (3)J(H, H), and (4)J(H, H) are calculated at the B3LYP/6-31G(d,p) level of theory. Their magnitude is explained in terms of electronic delocalization and the additivity of stereoelectronic effects.     

Syntheses of 1,3,6,8,10,11,14-heptaazapentaphene-2,4,7,9(14H,3H,8H, -11H)-tetrones (angular mixed flavins), 1,3,5,6,8,10,11,14-octaazapentaphene-2,4,7,9(14H,3H,8H,11H)-tetrones (angular doubled flavins), and their related compounds

Cyclization of N, N′-dialkyl-N-(3-methyluracil-6-yl)-N′-(5-nitro-3-methyluracil-6-yl)- p-phenylenediamines with the Vilsmeier reagent gives the corresponding 1,3,6,8,10,11,14-heptaazapentaphene-2,4,7,9-(14H,3H,8H,-11H) -tetrones (angular mixed flavins) 2. Cyclization of N, N′-di(5-nitro-3-methyluracil-6-yl)-p-phenylenedi-amines with the Vilsmeier reagent gives the corresponding 1,3,5,6,8,10,11,14-octaazapentaphene-2,4,7,9-(14H,3H,8H,11H)-tetrones (angular doubled flavins) 11 along with the angular mixed flavins 2.     

Dynamically biased statistical model for the ortho/para conversion in the H(2)+H(3) (+) → H(3) (+)+ H(2) reaction

In this work we present a dynamically biased statistical model to describe the evolution of the title reaction from statistical to a more direct mechanism, using quasi-classical trajectories (QCT). The method is based on the one previously proposed by Park and Light [J. Chem. Phys. 126, 044305 (2007)]. A recent global potential energy surface is used here to calculate the capture probabilities, instead of the long-range ion-induced dipole interactions. The dynamical constraints are introduced by considering a scrambling matrix which depends on energy and determine the probability of the identity/hop/exchange mechanisms. These probabilities are calculated using QCT. It is found that the high zero-point energy of the fragments is transferred to the rest of the degrees of freedom, what shortens the lifetime of H(5) (+) complexes and, as a consequence, the exchange mechanism is produced with lower proportion. The zero-point energy (ZPE) is not properly described in quasi-classical trajectory calculations and an approximation is done in which the initial ZPE of the reactants is reduced in QCT calculations to obtain a new ZPE-biased scrambling matrix. This reduction of the ZPE is explained by the need of correcting the pure classical level number of the H(5) (+) complex, as done in classical simulations of unimolecular processes and to get equivalent quantum and classical rate constants using Rice-Ramsperger-Kassel-Marcus theory. This matrix allows to obtain a ratio of hop/exchange mechanisms, α(T), in rather good agreement with recent experimental results by Crabtree et al. [J. Chem. Phys. 134, 194311 (2011)] at room temperature. At lower temperatures, however, the present simulations predict too high ratios because the biased scrambling matrix is not statistical enough. This demonstrates the importance of applying quantum methods to simulate this reaction at the low temperatures of astrophysical interest.     

Protonated clathrate cages enclosing neutral water molecules: (H+)(H2O)21 and (H+)(H2O)28

This paper describes a systematic study on the clathrate structure of (H+)(H2O)21 using tandem mass spectrometry, vibrational predissociation spectroscopy, Monte Carlo simulations, and density functional theory calculations. We produced (H+)(H2O)n from a continuous corona-discharged supersonic expansion and observed three anomalies simultaneously at the cluster temperature near 150 K, including (1) the peak at n=21 is more intense than its neighboring ions in the mass spectrum, (2) the size-dependent dissociation fractions show a distinct drop for the 21-mer, and (3) the infrared spectrum of (H+)(H2O)21 exhibits only a single feature at 3699 cm(-1), corresponding to the free-OH stretching of three-coordinated water molecules. Interestingly, the anomalies appear or disappear together with cluster temperature, indicating close correlation of these three observations. The observations, together with Monte Carlo simulations and density functional theory calculations, corroborate the notion for the formation of a distorted pentagonal dodecahedral (5(12)) cage with a H2O molecule in the cage and a H3O+ ion on the surface for this "magic number" water cluster ion. The dodecahedral cage melts at higher temperatures, as evidenced by the emergence of a free-OH stretching feature at 3717 cm(-1) for the two-coordinated water in (H+)(H2O)21 produced in a warmer molecular beam. Extension of this study to larger clusters strongly suggests that the experimentally observed isomer of (H+)(H2O)28 is most likely to consist of a distorted protonated pentakaidecahedral (5(12)6(3)) cage enclosing two neutral water molecules.     

Zur Kenntnis der Substitutionsprodukte der (2H)-Imidazol-4(3H)-thione und 2H-Imidazol-4(3H)-one

2H-Imidazole-4(3H)-thiones (a), available from methyl alkyl and methyl aryl ketones with sulfur and ammonia, react via their corresponding N-sodium compounds or in presence of tert. amines with alkyl and aryl carboxylic acid chlorides to give the corresponding intensely coloured (orange to violett) cryst. 3-acyl-2H-imidazole-4(3H)-thiones4 a-q and6–26. With dicarboxylic acid dichlorides the colourless cryst. N,N′-diacyl-bis-3-imidazoline-5-thiones5 a-d and27–32 are obtained. With carbamic acid chlorides and chloroformic acid esters the corresponding urea (33–35) and urethane derivatives36, 37 are formed. In an analogous way 2H-imidazol-4(3H)-ones react with acid chlorides to 3-acyl-2-imidazol-4(3H)-ones (44–50), which can also be obtained by treating the corresponding 3-acyl-2H-imidazole-4(3H)-thione with KMnO₄.     

Syntheses of 1,3,8,10,12-pentazanaphthacene-2,4,7,9-(12H,3H,8H,10H)-tetraones (linear pyrimidine-fused 5-deazaflavins), 1,3,6,8,12-pentazabenz[a]anthracene-2,4,7,9(12H,3H,6H,8H)-tetraones(bent pyrimidine-fused 5-deazaflavins), and their flavin analogs

1,3,8,10,12-Pentazanaphthacene-2,4,7,9(12H,3H,8H,10H)-tetraones (linear pyrimidine-fused 5-deazaflavins) and 1,3,6,8,12-pentazabenz[a]anthracene-2,4,7,9(12H,3H,6H,8H)-tetraones (bent pyrimidine-fused 5-deazaflavins) were synthesized by condensation of 7-alkylaminoquinazoline with 6-chloro-5-formyl-3-methyluracil. Also, their flavin analogs, 1,3,5,8,10,12-hexazanaphthacene-2,4,7,9(12H,3H,8H,10H)-tetraones (linear pyrimidine-fused flavins) and l,3,5,6,8,12-hexazabenz[a]anthracene-2,4,7,9(12H,3H,6H,8H)-tetraones (bent pyrimidine-fused flavins) were synthesized by cyclization of 7-[N-alkyl-N-(5-nitrouracil-6-yl)]aminoquin-azolines with the Vilsmeier reagent.     

NMR studies of 4(3H)-quinazolinones and 4(3H)-quinazolinethiones

Summary Unambiguous¹H and¹³C NMR assignments for 4(3H)-quinazolinones1–6 and their corresponding 4-thiones7–12 have been made. This resulted in the revision of the previous assignments for the two benzenoid carbons (C-5 and C-8) of quinazolinones1,2,4, and5. Thionation of the nucleophilic amides1–6 has been found to cause a distinct change in the¹³C chemical shift of particularly C-4, but also of those of C-4a, C-5, and C-8a. One-bond and several long range heteronuclear coupling constants for the compounds have also been measured.

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Kernresonanzspektroskopie von 4(3H)-Chinazolinonen und 4(3H)-Chinazolinthionen

Zusammenfassung Die¹H- und¹³C-NMR-Spektren der 4(3H)-Chinazolinone1–6 und ihrer entsprechenden 4-Thione7–12 wurden zugeordnet. Dabei zeigte sich, daß eine frühere Zuordnung der beiden benzoiden Kohlenstoffe (C-5 und C-8) der Chinazolinone1,2,4 und5 falsch war. Ersatz des Sauerstoffs durch Schwefel in den nukleophilen Amiden1–6 führt insbesondere für C-4, aber auch für C-4a, C-5 und C-8a zu einer deutlichen Änderung der chemischen Verschiebung. Heteronukleare Kopplungskonstanten über eine und über mehrere Bindungen wurden bestimmt.

     

6(5H)-phenanthridinones. III. halo-6(5H)phenanthridinones

Halogenation of 6(5H)-phenanthridinone or its 3,8-dihalo derivatives with N-bromo or N-chlorosuccinimide in dimethylformamide gives the corresponding 2-halophenanthridinones (I,V,XI-XIV). Further halogenation of 2-halo-6(5H)-phenanthridinone with the appropriate N-halosuccinimide, in the same medium, gives the corresponding 2,4-dihalo derivatives (II,VI). NXS/DMF is found to be a very convenient halogenating system in these preparations. 1,3,8-Trihalo-6(5H)-phenanthridinones (XIX,XX) are prepared from the 1-nitro derivatives which are obtained by a Schmidt rearrangement of 2,7-dihalo-4-nitro-9-oxofluorenes. Similarly, rearrangement and further reaction of 2-nitro-5-chloro-9-oxofluorene (XXI) leads to 3,10-dichloro-6(5H)-phenanthridinone (XXIV). UV absorptions as well as selected IR absorptions of these 6(5H)-phenanthridinones are described.     

Synthesis of 1,3,7,9,11,12,14-heptazapentacene-2,4,8,10-(14H,3H,9H,12H)-tetraones (mixed flavins) with oxidizing ability

1,3,7,9,11,12,14-Heptazapentacene-2,4,8,10(14H,3H,9 H,12H)-tetraones (mixed flavins) were synthesized by the cyclization of 1,5-dihydro-8-[N-alkyl-N-(5-nitrouracil-6-yl)]-amino-5- deazaflavins with the Vilsmeier reagent. The mixed flavins oxidized alcohol under neutral conditions in sunlight.     

Coherent excitation of H(n=2) in H+, H - He collisions

The coherent excitation of H(n=2) in H⁺, H - He collisions was investigated at incident energies of 5–25 keV. From a polarization analysis of the emitted Lyman-α radiation as a function of an external electric field, the partial cross sections for excitation to the H(2s) and the H(2p _m) magnetic substates and the real part of thes ?p ₀-coherence were extracted. For H⁺-He collisions, the measured partial cross sections are in fair agreement with previous two-electron calculations by Kimura and Lin; the agreement with one-electron calculations of Jain et al. is, particularly at the lower incident energies, less satisfactory. For both collision systems, an energy-dependent forward-backward asymmetry corresponding to a shift of the center-of-charge relative to the center-of-mass (dipole moment) was observed. In H⁺ - He collisions, the measured dipole moment was positive; it thus corresponds to an electron trailing behind the proton. The same analysis applied to the H - He system showed the electron riding in front of the proton.     

Cyanoferrat(H) neben Cyanid

Ohne Zusammenfassung     

Unique {H(SiR(3))(2)}, (H(2)SiR(3)), H(HSiR(3)), and (H(2))SiR(3) ligand sets supported by the {Fe(Cp)(L)} platform (L=CO, PR(3))

This work deals with the type and incidence of nonclassical Si--H and H--H interactions in a family of silylhydride complexes [Fe(Cp)(OC)(SiMe(n)Cl(3-n))H(X)] (X=SiMe(n)Cl(3-n), H, Me, n=0-3) and [Fe(Cp)(Me(3)P)(SiMe(n)Cl(3-n))(2)H] (n=0-3). DFT calculations complemented by atom-in-molecule analysis and calculations of NMR hydrogen-silicon coupling constants revealed a surprising diversity of nonclassical Si--H and H--H interligand interactions. The compounds [Fe(Cp)(L)(SiMe(n)Cl(3-n))(2)H] (L=CO, PMe(3); n=0-3) exhibit an unusual distortion from the ideal piano-stool geometry in that the silyl ligands are strongly shifted toward the hydride and there is a strong trend towards flattening of the {FeSi(2)H} fragment. Such a distortion leads to short Si--H contacts (range 2.030-2.075 A) and large Mayer bond orders. A novel feature of these extended Si--H interactions is that they are rather insensitive towards the substitution at the silicon atom and the orientation of the silyl ligand relatively the Fe--H bond. NMR spectroscopy and bonding features of the related complexes [Fe(Cp)(OC)(SiMe(n)Cl(3-n))H(Me)] (n=0-3) allow for their rationalization as usual eta(2)-Si--H silane sigma-complexes. The series of "dihydride" complexes [Fe(Cp)(OC)(SiMe(n)Cl(3-n))H(2)] (n=0-3) is different from the previous two families in that the type of interligand interactions strongly depends on the substitution on silicon. They can be classified either as usual dihydrogen complexes, for example, [Fe(Cp)(OC)(SiMe(2)Cl)(eta(2)-H(2))], or as compounds with nonclassical H--Si interactions, for example, [Fe(Cp)(OC)(H)(2)(SiMe(3))] (16). These nonclassical interligand interactions are characterized by increased negative J(H,Si) (e.g. -27.5 Hz) and increased J(H,H) (e.g. 67.7 Hz).     

One‐dimensional Cadmium(II) Coordination Polymers: Syntheses and Crystal Structures of [Cd(H2O)3(C5H6O4)]·2H2O,Cd(H2O)2(C6H8O4), and Cd(H2O)2(C8H12O4)

[Cd(H₂O)₃(C₅H₆O₄)]·2H₂O ( 1 ) and Cd(H₂O)₂(C₆H₈O₄) ( 2 ) were prepared from reactions of fresh CdCO₃ precipitate with aqueous solutions of glutaric acid and adipic acid, respectively, while Cd(H₂O)₂(C₈H₁₂O₄) ( 3 ) crystallized in a filtrate obtained from the hydrothermal reaction of CdCl₂·2.5H₂O, suberic acid and H₂O. Compound 1 consists of hydrogen bonded water molecules and linear {[Cd(H₂O)₃](C₅H₆O₄)_2/2} chains, which result from the pentagonal bipyramidally coordinated Cd atoms bridged by bis‐chelating glutarato ligands. In 2 and 3 , the six‐coordinate Cd atoms are bridged by bis‐chelating adipato and suberato ligands into zigzag chains according to {[Cd(H₂O)₃](C₅H₆O₄)_2/2} and {[Cd(H₂O)₂](C₈H₁₂O₄)_2/2}, respectively. The hydrogen bonds between water and the carboxylate oxygen atoms are responsible for the supramolecular assemblies of the zigzag chains into 3D networks. Crystallographic data: ( 1 ) P1¯ (no. 2), a = 8.012(1), b = 8.160(1), c = 8.939(1) Å, α = 82.29(1)°, β = 76.69(1)°, γ = 81.68(1)°, U = 559.6(1) ų, Z = 2; ( 2 ) C2/c (no. 15), a = 16.495(1), b = 5.578(1), c = 11.073(1) Å, β = 95.48(1)°, U = 1014.2(1) ų, Z = 4; ( 3 ) P2/c (no. 13), a = 9.407(2), b = 5.491(1), c = 11.317(2) Å, β = 95.93(3)°, U = 581.4(2) ų, Z = 2.