Pteridine studies: III—13C n.m.r. data of pteridine,some of its derivatives and their covalent σ-adducts with ammonia and water

¹³C n.m.r. spectral data of pteridine and nineteen of its derivatives (containing one or more chloro, methylthio, methyl, t-butyl or phenyl substituents) are reported. The ¹³C n.m.r. spectrum of the title compound has been assigned conclusively. ¹³C n.m.r. substituent effects are shown to be very useful in discerning between 6- and 7-substituted pteridines. Additionally, the ¹³C n.m.r. spectra of several covalent amination products, i.e. the 3,4-dihydro-4- amino- and the 5,6,7,8-tetrahydro-6,7-diaminopteridine derivatives, formed by dissolving the appropriate pteridine in liquid ammonia, have been recorded. The ¹³C n.m.r. spectra of the corresponding covalent hydrates are also reported.     

1H and 13C studies of alkenes,epoxides and cyclic thionocarbonates

¹H and ¹³C chemical shift data are presented and discussed for a number of di- and tri-alkyl substituted alkenes, epoxides and thionocarbonates. The completely stereospecific interconversion of these compounds, together with the n.m.r. data, allows a straightforward and quantitative stereochemical analysis. For ¹H n.m.r., the most useful intermediates proved to be the thionocarbonates. The differential shieldings between cis and trans isomers are tentatively explained in terms of the conformational change of the 5-membered thionocarbonate ring. In ¹³C n.m.r., either series can be useful to distinguish between stereoisomers. The conclusions stemming from the ¹³C n.m.r. results complement the ¹H n.m.r. studies.     

1H-Festkörper-NMR-Untersuchungen am synthetischen Pektolith Ca2NaHSi3O9

Solid-state ¹H N.M.R. Studies of Synthetic Pectolite Ca₂NaHSi₃O₉ A synthetic pectolite Ca₂NaHSi₃O₉ is studied by means of conventional ¹H pulse-fourier-transform wide line n.m.r. and methods of solid-state high-resolution ¹H n.m.r. (MREV8 multiple pulse technique, combined multiple pulse magic angle spinning experiments). The n.m.r. spectra consist of a dominant signal due to SiOH groups and a small signal which can be assigned to water molecules. The parameters of the ¹H n.m.r. spectra for the SiOH groups are discussed in comparison with the known structure of pectolite. It can be shown that the structural details for the proton of the SiOH groups are reflected by the ¹H n.m.r. spectra.     

1H- und 13C-NMR-untersuchungen an dibromoxabicyclo[n.2.1]alkanen

The ¹H n.m.r. spectra of some dibromooxabicyclo[n.2.1]alkanes are discussed for the determination of the configuration and conformation. The ¹³C n.m.r. spectra confirm the observed stereochemistry. With increasing ring size the ¹³C n.m.r. chemical shifts of the hetero atom substituted C-atoms C-1 and C-2 move steadily to lower fields.     

13C n.m.r. spectroscopy: Comparison of the spectra of some dimeric Catharanthus alkaloids and their derivatives

The ¹³C n.m.r. spectra of some dimeric Catharanthus alkaloids are reported and assigned. Methods devised to aid in the assignment of resonances in complex molecules are described. The ¹³C n.m.r. spectra of several derivatives of vinblastine are discussed.     

Synthesis and spectral studies ofo-hydroxyacetophenone (N-benzoyl)glycyl hydrazone and some of its lanthanide(III) complexes

Summary o-Hydroxyacetophenone (N-benzoyl)glycyl hydrazone (o-HABzGH) has been characterized by i.r.,¹H n.m.r.,¹³C n.m.r. and mass spectral studies, and its complexes of the types [Ln(o-HABzGH)Cl₂(H₂O)₂]Cl and [Ln(o-HABzGH–2H)OH(H₂O)₃], where Ln=La, Pr, Nd, Sm and Eu, have been synthesized. The structures of the complexes have been studied by conductance, magnetic, electronic, i.r.,¹H n.m.r. and¹³C n.m.r. spectral techniques. The hypersensitive bands of the electronic spectra suggest coordination numbers six and seven around Nd^III in its adduct and neutral complexes respectively. I.r. and n.m.r. spectral data suggest a neutral bidentate behaviour for the ligand in the adducts and a dinegative tridentate nature in the neutral complexes.     

Über die Reaktion von Thiophosphoryltrichlorid mit Hexamethyldisilazan

On the Reaction of Thiophosphoryl Chloride with Hexamethyl Disilazane On the basis of a ³¹P n.m.r. spectroscopic study of the reaction of PSCl₃ with hexamethyl disilazane a method for the preparation of Me₃SiNHP(S)Cl₂( 1 ) and the diazadiphosphetidine 2 , [Me₃SiNHP(S)?NSiMe₃]₂ has been developed. These new crystalline compounds have been characterized by i.r., Raman, ³¹P n.m.r. and mass spectroscopy, and their thermal behaviour has been studied. The formation and constitution of 2 are discussed, and its ¹H and ²⁹Si n.m.r. spectra are reported.     

Preparation and characterization of some stable acyclic oxyphosphoranes

A series of phosphoranes containing the hexafluoroisopropoxy group has been synthesized and characterized by ¹H, ¹⁹F, and ³¹P n.m.r., and by mass spectrometry. Some variable temperature n.m.r. studies are reported and the results are discussed in terms of possible ground state structures of the phosphoranes.     

NMR-Untersuchungen an Dicyclopentadienderivaten: III—Stereochemische Zuordnung von überbrückten endo-Dicyclopentadienderivaten und deren Wagner-Meerwein-Umlagerungs-produkten mit Hilfe der NMR-Spektroskopie

The ¹H n.m.r. spectra of some substituted oxa- and azatetracycloundecanes are studied and selected examples analysed in detail with the aid of spin-spin decoupling and Eu(fod)₃ paramagnetic shift experiments. From the quoted ¹³C n.m.r. spectra the carbon resonances are assigned, using known substituent effects and paramagnetic shift values. The determined paramagnetic shift parameters ΔEu are discussed in respect of their contact and pseudocontact contributions.     

Silver Cyanide Complexes of Heterocyclic Thiones

Silver(I) cyanide complexes of various thiones (imidazolidine-2-thione, diazinane-2-thione and their derivatives) have been prepared and characterized by elemental analysis, i.r. and n.m.r. (¹H, ¹³C, ¹⁵N and ¹⁰⁷Ag) spectroscopy. It appears from the i.r. data that six out of the ten complexes are nonionic [>C=S—Ag—CN] while the remaining four exist as ionic species [Ag(>C=S)₂]⁺[Ag(CN)₂]^– in the solid state. An upfield shift in the ¹³C-n.m.r. and downfield shifts in the ¹H-, ¹⁵N- and ¹⁰⁷Ag-n.m.r. spectra are consistent with the sulfur coordination to silver(I). The n.m.r. data shows that the [>C=S—AgCN] complexes are stable in solution and do not undergo redistribution.     

N.m.r. spectra of prostaglandin metabolites and precursors and of related pyrazoline adducts

The ¹³C n.m.r. spectra of the major human urinary metabolite of prostaglandin PGE₂ and PGE₁ are discussed together with some unsaturated precursors. Δ-2-Pyrazolines, formed by addition of diazomethane to the 11-oxo dienediones in this series, were identified by ¹³C and ¹H n.m.r. and by other physical methods.     

Crystal structure of [Cu4(pytp)2(SO4)2(H2O)10](SO4)2 · 4H2O. A tetranuclear copper(II) complex with a new asymmetric ligand,pytp*, as a bridge

A new asymmetric bridge ligand, pytp, was prepared and characterized systematically by f.t.i.r., u.v.–vis., ¹H-n.m.r. and by FAB-MS spectroscopy. A tetranuclear Cu^II complex [Cu₄(pytp)₂(SO₄)₂(H₂O)₁₀](SO₄)₂·4H₂O (1) was prepared and characterized by elemental analysis and u.v.–vis. spectroscopy. A crystal structure analysis indicates that there are two different coordination spheres in (1) and that two of the copper centers are bridged by two ₂-SO₄ entities, creating a most unusual sulphate bridge.     

Nuclear magnetic resonance spectral study of 2-acetylpyridine4 N-alkylthiosemicarbazones and their cobalt(III) complexes

¹H and¹³C n.m.r. spectra are reported for a series of 2-acetylpyridine⁴ N-alkylthiosemicarbazones in order to study the effect of increased size of the alkyl function on the ratio of isomers present in solution. Similarly, n.m.r. data for the bis(thiosemicarbazone)cobalt(III) complexes are included, as well as these complexes' ligand field parameters. TMC 2698     

Iterative least-squares analysis of dynamic n.m.r. spectra. Hindered rotation of the N-nitroso group in N-nitroso-N-cyanomethylmethylamine

Iterative analysis of dynamic n.m.r. (d.n.m.r.) spectra by the least-squares method was applied to the entire proton spectrum of N-nitroso-N-cyanomethylmethylamine and, separately, to the CH₃ and CH₂CN sub-spectra. Resulting differences in the estimated rates of rotation of the NO group are discussed in terms of systematic errors which may be involved in determining spin exchange rates by d.n.m.r. methods. The most probable explanation is that quadrupolar broadening and then unresolved ¹⁴N? ¹H spin–spin splitting may appear on increasing the temperature. Estimated entropies of activation indicate that the methyl sub-spectrum gives more reliable results.     

Temperature effects on 13C n.m.r. chemical shifts of normal alkanes and some line r and branched 1-alkenes

¹³C n.m.r. chemical shifts of a number of 1,1-disubstituted ethylenes are presented. Moreover, effects of changing temperatures on the ¹³C n.m.r. chemical shifts of some of these compounds as well as of three normal alkanes are given. These variations in chemical shifts are attributed to varying amounts of sterically induced shifts in the different conformational equilibria. In addition to the well-known 1,4 interaction between two alkyl groups shielding effects on the carbon atoms of the connecting bonds are also proposed. No definite explanation of this effect is presented at this time. It is further shown that no simple correlations exist between ¹³C n.m.r. chemical shifts and calculated total charge densities at this level. Instead, the experimental results in 1-alkenes are rationalized by assuming a linear dependence of the ¹³C n.m.r. chemical shifts of C-1 and C-2 via rehybridizations on changes in bond angles for small skeletal deformations caused by steric interactions. These changes in geometries, as well as conformational energies in three 1-alkenes, were calculated by means of VFF calculations. Finally. upfield shifts for both C-2 and C-4 are proposed for those conformations of 1-alkenes in which the C-3? C-4 group interacts with the p_z-orbital of C-2.     

NMR-spektroskopische Untersuchungen an Fluoro-diaza-diphosphetidinen und Fluoro-λ5-monophosphazenen

N.M.R. Investigations of Fluorodiazadiphosphetidines and Fluoro-λ⁵-monophosphazenes The ¹⁹F and ³¹P n.m.r. data of 37 fluorodiazadiphosphetidines [RR′PF? NC₆H₄X]₂, and 62 fluoro-λ⁵-monophosphazenes, RR′PF=NC₆H₄X, are submitted. In the case of tetrafluorodiazadiphosphetidines, [RPF₂? NC₆H₄X]₂, an intramolecular exchange of the fluorine atoms at phosphorus has to be concluded from the n.m.r. data. The influence of the substituents R and X on the n.m.r. parameters is discussed using simple models of molecular structure.     

NMR-Untersuchungen an Dicyclopentadienderivaten. IV—1-Syn/anti-Epimere von endo-Dicyclopentadienderivaten

The syn/anti-arrangement of some substituents R in position 1 of endo-dicyclopentadiene derivatives is investigated by ¹H-and ¹³C n.m.r. spectroscopy. The HH-coupling constants of the epimeric alcohols 2 and 3 are determined by paramagnetic shift experiments [Eu(fod)₃] and the observed relative paramagnetic shifts ΔEu used for the determination of the configuration. The increasing steric compression in the syn-epimers is well reflected by the ¹H- and ¹³C n.m.r. chemical shifts.     

Benzofurobenzthiazole: VI—1H- und 13C-NMR-Spektren von 2-Aminobenzofuro[2,3-f] benzthiazol und 2-Aminobenzofuro[2,3-e]benzthiazol im Vergleich mit Dibenzofuran und 2-Aminobenzthiazol

Cyclization of 3-dibenzofurylthiourea under the conditions of the Hugershoff reaction gives the linear structure 1. ¹H n.m.r. and ¹³C n.m.r. spectra of the two isomeric aminobenzofurobenzothiazoles (1 and 3), recorded at 220 MHz, 60 MHz and 22,62 MHz respectively, were used as aids for the structure determination. The magnetic parameters were obtained partly by first-order analysis and partly by simulation of spectra using LAOCOON 3. The assignments were made by comparing the chemical shifts and coupling constants with those of the parent compounds dibenzofuran (4a) and 2-aminobenzothiazole (5c). In so far as the assignments of ¹H n.m.r. and ¹³C n.m.r. frequencies of the parent compounds themselves were unknown or supported by analogy only, they have been determined using experimental criteria such as deuterium substitution and investigation of changes in chemical shifts caused by derivation.     

Sulfated titania catalyzed water mediated efficient synthesis of dicoumarols—a green approach

An efficient, mild, and environmental friendly method has been developed for the synthesis of dicoumarols in water over Lewis and Bronsted acid catalyst sulfated titania (TiO₂/SO₄²⁻). The method involves the condensation of various aromatic and aliphatic aldehydes with 4-hydroxycoumarin. It affords the corresponding product in high yield with short reaction times employing a very low loading of catalyst. The catalyst was reused several times without significant change in activity.     

Die Reduktion von Germanium- und Zinntetrabromid durch Tri-tert-butylphosphin: Brom-tri-tert-butylphosphonium-Salze

Reduction of Germanium and Tin Tetrabromide by Tri-tert-butylphosphine: Bromo-tri-tert-butylphosphonium Ions Tri-tert-butylphosphine react with equimolar amounts of germanium or tin tetrabromide with formation of “1:1 adducts”. The new compounds are characterized as bromo-tri-tert-butylphosphonium salts (t-C₄H₉)₃PBr⁺MBr₃^? by ¹H n.m.r., ³¹P n.m.r., infrared and Raman spectroscopy (M = Ge, Sn).