Beiträge zur Chemie der Pyrrolpigmente,LVIII Phytochrommodellstudien: Konformationsanalytische Untersuchungen an 2,3-Dihydrobilatrien-abc-Derivaten

Two 3,4-dihydropyrromethenones and two 2,3-dihydrobilatrienes-abc O-methylated at rings A and D resp. have been prepared. Their configurations were established as (Z), (E), (Z, Z, Z) and (Z, Z, Z), respectively, using¹H-NMR-techniques (NOE); they are also shown to exist predominantly in the lactam form. Within the pyrromethene fragment of the bilatrienes the pyrrolic and pyrroleninic ring type depends on the position of O-methylation. A helical all-synperiplanar conformation in solution could be established for all cases by applying the lanthanide induced shift (LIS) technique.

     

Quantitative analysis of deuterium using the isotopic effect on quaternary C NMR chemical shifts

Quantitative analysis of specifically deuterated compounds can be achieved by a number of conventional methods, such as mass spectroscopy, or by quantifying the residual ¹H NMR signals compared to signals from internal standards. However, site specific quantification using these methods becomes challenging when dealing with non-specifically or randomly deuterated compounds that are produced by metal catalyzed hydrothermal reactions in D₂O, one of the most convenient deuteration methods. In this study, deuterium-induced NMR isotope shifts of quaternary ¹³C resonances neighboring deuterated sites have been utilized to quantify the degree of isotope labeling of molecular sites in non-specifically deuterated molecules. By probing ¹³C NMR signals while decoupling both proton and deuterium nuclei, it is possible to resolve ¹³C resonances of the different isotopologues based on the isotopic shifts and the degree of deuteration of the carbon atoms. We demonstrate that in different isotopologues, the same quaternary carbon, neighboring partially deuterated carbon atoms, are affected to an equal extent by relaxation. Decoupling both nuclei (¹H, ²H) resolves closely separated quaternary ¹³C signals of the different isotopologues, and allows their accurate integration and quantification under short relaxation delays (D1 = 1 s) and hence fast accumulative spectral acquisition. We have performed a number of approaches to quantify the deuterium content at different specific sites to demonstrate a convenient and generic analysis method for use in randomly deuterated molecules, or in cases of specifically deuterated molecules where back-exchange processes may take place during work up.     

Cyclodextrin inclusion of four phenylurea herbicides: determination of complex stoichiometries and stability constants using solution 1H NMR spectroscopy

An inclusion complex formation between α- and β-cyclodextrin and four phenylurea analogues, namely metobromuron, monolinuron, monuron and fenuron, is reported. Complex formation was established using solution ¹H NMR spectroscopy. Complex stoichiometries were determined by the method of continuous variation using the chemically induced shifts of both the host and guest protons. An analysis of the spectroscopic data revealed the stoichiometry as 1:1 in all cases while a further analysis of the same data yielded values for the association constant K ranging from 208 to 2749 M^? 1. From the observed chemical shifts it was deduced that in all cases, only the guest aromatic ring enters the host cavities, the substituted urea moiety protruding from the secondary rim in the case of α-cyclodextrin, but from the primary rim in the case of β-cyclodextrin.     

Stereochemie von Metallocenen, 43. Mitt.: Torsionsisomere Biphenyl-tricarbonylchrom-Komplexe: Darstellung,Konformationsanalyse und Kinetik der Interkonversion

Complexation of methyl 3-nitro-2-(o-tolyl)-benzoate (2, ano-trisubstituted biphenyl) with hexacarbonyl chromium gave the isomeric Cr(CO)₃ complexes3 and4 both existing as two torsional isomersa andb, as seen by nmr. For the main product3 the preferred conformations of the two torsional isomersa andb were deduced by the lanthanide induced shift (LIS) technique. The activation energy for the interconversion process could be determined from kinetic measurements and especially from¹H-nmr coalescence temperature of the methylsignals. The barrier of 91±1.5 kJ/mol (21.7±0.3 kcal/mol) in3 reflects the interaction of theo-H-atom of the benzene ring passing the Cr(CO)₃ moiety of the benchrotrene ring during the interconversion.A partial optical resolution of3 was achieved by asymmetric reduction with a chiral lithium-aluminium hydride yielding (+)-3 with [] _D ²⁰ +30° (benzene) and the levorotatory alcohol (–)-7.

42. Mitt.:K. Schlögl undR. Schölm, Mh. Chem.109, 1227 (1978).     

Zur Struktur der Produkte der Reaktion vonE/Z-1-Benzolsulfonyl-3-(1-pentenyl)-indol mit N-Phenylmaleinimid: Ein erster Beitrag zur Konfigurations- und Konformationsanalyse in der Vinylindol-Cycloadditionsreihe

The products2,3 of the reaction ofE/Z-1-benzenesulfonyl-3-(1-pentenyl)-indole (1) and N-phenylmaleimide were analysed by¹H-NMR spectroscopy. Exemplarily, the structure elucidation of theendo-cyclo-adduct2 b was achieved by using several NMR techniques (diff. NOE-, INDOR-measurements, decoupling experiments, spectra simulation). The¹H-NMR-spectroscopically gained prediction of relative configuration and conformation of2 b was supported on X-ray analysis. The cyclohexene ring of the new cycloadducts adopts in the liquid phase and in the crystal a slightly twisted boat conformation.

     

Beiträge zur Stereochemie der Additionsreaktionen an 3,4,5,6-Tetrahydropyridin-1-oxide. 2. Mitt.

4-tert-Butyl-3,4,5,6-tetrahydropyridine-1-oxide (1) and 6-butyl-3,4,5,6-tetrahydropyridine-1-oxide (2) were prepared and isolated in their monomeric forms. In many aprotic solvents these compounds are converted into their dimers. The main product in both cases is the addition product of identical enantiomers. In the case of compound1 a very small amount of an addition product of the optical antipodes is also formed, which is the thermodynamically most stable isomer. In contrast, compound2 yielded an addition product of the optical antipodes in larger amounts, with a thermodynamically less favourable structure. These dimerizations are solvent dependent, reversible and sensitive to steric hindrance.

     

Phosphate Derivatives of Natural Lactones. I. Synthesis of Novel Isoalantolactone Dialkylphosphonates

Novel isoalantolactone dialkylphosphonates were synthesized in 70-87% yields by reacting this eudesmanolide with dialkylphosphites. Their structures were proved by spectral analysis using IR, PMR, ¹³C and ³¹P NMR, and two-dimensional ¹H-¹H (COSY) spectroscopy. The reaction of isoalantolactone with dialkylphosphites is highly stereoselective.     

Albartin—a new sesquiterpene-coumarin ether fromArtemisia alba

A new sesquiterpene isofraxidin ether (isofraxidin=7-hydroxy-6,8-dimethoxy-coumarin) was isolated from the roots ofArtemisia alba and characterized by means of¹H-nmr,¹³C-nmr, ms, uv, and ir. Albartin is an exomethylene isomer of 3-acetyloxy-drimartol isofraxidin ether with -OAc axial and -CH₂OAr equatorial. The chemosystematic significance of this class of compounds within the genusArtemisia is briefly discussed.

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Albartin — ein neuer Sesquiterpen-Cumarin-Ether ausArtemisia alba (Kurze Mitteilung)

Zusammenfassung Aus den Wurzeln vonArtemisia alba wurde ein neuer Sesquiterpen-Isofraxidin Ether (Isofraxidin = 7-Hydroxy-6,8-dimethoxy-cumarin) isoliert und mittels¹H-NMR,¹³C-NMR, MS, UV und IR charakterisiert. Albartin ist ein exo-Methylen-Isomer von 3-Acetyloxy-drimartol-isofraxidin-ether mit-OAc axial und -CH₂OAr equatorial. Die chemosystematische Bedeutung dieser Verbindungsklasse innerhalb der GattungArtemisia wird kurz diskutiert.

     

Naphthopyrones,Part I Proton magnetic resonance spectral studies of some methylnaphthopyran-2-one and methylnaphthopyran-4-one derivatives

The 220 MHz¹H-NMR spectra of four methylnaphthopyrone derivatives are presented and discussed. The chemical shift changes which occur upon protonation in trifluoroacetic acid solution are much more significant for the benzochromones than for the benzocoumarins. The particularly large effects at the methyl (0.6 ppm) and at the residual pyrone ring proton (1.2 ppm) provide a useful technique for differentiation between the two series of compounds.

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Naphthopyrone, 1. Mitt.:¹H-N M R einiger Methylnaphthopyran-2-one und Methylnaphthopyran-4-one

Zusammenfassung Es werden die 220 MHz¹H-NMR-Spektren von vier Methylnaphthopyronen diskutiert. Die Änderungen der chemischen Verschiebungen, die sich mit Trifluoressigsäure als Lösungsmittel ergeben, sind für die Benzochromone bedeutend signifikanter als für Benzocumarine. Die besonders großen Effekte für Methyl (0,6 ppm) und das verbleibende Pyronringproton (1,2 ppm) stellen eine brauchbare Methode für die Unterscheidung der beiden Reihen dar.

     

Correlation NMR spectroscopy of 1,1-dichloro-2,3,4,5-tetraphenyl-1-germacyclopenta-2,4-diene

Assignment of all of the signals in the¹H and¹³C NMR spectra of 1,1-dichloro-2,3,4,5-tetraphenyl-l-germacyclopenta-2,4-diene has been carried out using two-dimensional NMR spectroscopy. Translated fromIzvestiya Akademii Nauk Seriya Khimicheskaya, No. 3, pp. 623–625, March, 1997.     

Synthese,Kristallstruktur und Konformation von N2-Dibenzyl-N1-t-butoxycarbonylhydrazin

Summary The synthesis and the crystal structure of N²-dibenzyl-N¹-butoxycarbonyl hydrazine are reported. The compound was prepared from commercially availablet-butyl carbazate. It crystallizes in the triclinic space group P 1 witha=5.479(1) Å,b=9.559(1) Å,c=9.748(1) Å,a=63.81(1)°, =87.52(1)°, =74.07(1) Å,Z=1,D=1.18 g/cm³. The structure was solved by direct methods and refined toR=0.0329.

     

Polysaccharides of Fabaceae. I. Galactomannan of Astragalus sericeocanus seeds

Galactomannan (yield 3.58% of seed mass) of molecular weight 876 kDa was isolated from seeds of Astragalus sericeocanus Gontsch. (Fabaceae). Its solutions had high viscosity [η], 764.6 mL/g, and optical density [α]_D +65.3°. The polysaccharide consisted of galactose and mannose in molar ratio 1:1.58. The main chain of the galactomannan macromolecule was constructed of 1,4-β-D-mannopyranose units, 63% of which were substituted at C-6 by single α-D-galactopyranose units. ¹³C NMR spectroscopy established that the galactomannan contained units of differently substituted galactose mannobiose units: Man-Man, (Gal)Man-Man, and/or Man-Man(Gal) in addition to (Gal)Man-Man(Gal), the ratio of which was 0.15:0.51:0.34. Translated from Khimiya Prirodnykh Soedinenii, No. 6, pp. 555–557, November–December, 2008.     

2-Polyfluoroalkylchromones. 12. Nitration of 5,7-dimethyl-2-polyhaloalkylchromones and complete assignment of signals in the 1H and 13C NMR spectra of 5,7-dimethyl-2-trifluoromethylchromone and its mono- and dinitro derivatives

The nitration of 5,7-dimethyl-2-polyhaloalkylchromones affords either 5,7-dimethyl-6-nitro- or 5,7-dimethyl-6,8-dinitro-2-polyhaloalkylchromones, depending on the reaction conditions. Signals in the ¹H and ¹³C NMR spectra of the sterically hindered chromones were completely assigned using the 2D NOESY, HETCOR, and COLOC spectra. The influence of nonplanar nitro groups on chemical shifts of carbon atoms was studied. Some spectral peculiarities of the peri-methyl group were revealed. The ¹H-¹H and ¹³C-¹H spin-spin coupling constants, including the extreme six-bond long-range coupling between the protons of the Me(5) group and H(8), were determined.     

Modelluntersuchungen zur Simulierung von LIS. II.1 2-, 3-und 7-substituierte 1-Indanone

The space close to the coordination site of1-indanone is modified systematically by placing alkyl groups of different bulkiness on C-2, C-3 and C-7, resp. The¹H-LIS for the compounds are interpreted using the one site and two site model for carbonyl. Precautionary measures are discussed for both models to give reliable results in the calculation.

Herrn Prof.O. E. Polansky mit den besten Wünschen zum 60. Geburtstag gewidmet.     

REDUCTION OF NITROGEN FUNCTIONAL GROUPS WITH ELEMENTAL SULFUR IN LIQUID AMMONIA AND AMINES

Abstract

Nitrosobenzene and phenylhydroxylamine were reduced with elemental sulfur in liquid ammonia and amines to give aniline as the major product. Although hydrazobenzene was obtained by the reactions of azoxybenzene and azobenzene with elemental sulfur in liquid ammonia and amines, the expected aniline was not obtained. The utilities of elemental sulfur in liquid ammonia and amines as reductant is discussed.     

1H, 13C,and 14N NMR study of 3-methylfurazans with nitrogen-containing substituents at position 4

3-Methylfurazans with nitrogen-containing substituents at position 4 were studied by ¹H, ¹³C, and ¹⁴N NMR spectroscopy. A correlation between the chemical shifts in ¹³C NMR spectra of these furazans and monosubstituted benzenes with the same substituents was found. The increments for a number of furazan-containing substituents were determined for the first time.     

A.c. impedance behaviour of processes involving adsorption and reactivity of guanidonium-type cations at Pt(1 0 0) surface

The present paper reports a.c. impedance spectroscopic studies on adsorption of guanidonium (G⁺) and N,N-dimethylguanidonium (DMG⁺) resonant cations at Pt(1 0 0) single-crystal surface. The resulted information provided confirmation of the role of electrosorption of the above-mentioned molecule–ions through evaluation of the associated charge-transfer resistances and capacitances for the Pt(1 0 0) plane in 0.5 M H₂SO₄. These results also provided support for the interfacial ion-pairing mechanism that had been based on the voltammetric and in situ FTIR spectroscopic results published earlier.     

Model calculations on LIS,III. A simple force field model for Ln(III)-shift-reagent—Substrate complexes, 1. Carbinols

A force field type of calculation (FFLIS model, force field aided LIS calculation) is presented allowing to predict the lanthanide(III) positionand the relative LIS values for carbinol—Ln(III) complexes.II.:O. Hofer, Mh. Chem.110, 745 (1979).     

Conformational analysis by LIS. II. 2-and 3-alkyl substituted 1-indanones

The preferred conformations of the alkyl groups relative to the cyclopentenone ring of 2-ethyl-, 2-benzyl-, 2-isopropyl-, and 3-isopropyl-1-indanone were determined by means of the lanthanide-induced-shift technique (LIS). Two different models were used in the calculation of LIS. Coupling data-where available-were compatible with the conformations derived from LIS data. O. Hofer, Mh. Chem.109, 405 (1978).     

Reactions of 1-aryl-2-bromodiazene 1-oxides with acids and bases

The reactions of 1-aryl-2-bromodiazene 1-oxides with HCl in nonaqueous media give aryldiazonium chlorides, while 1,3,3-substituted triazenes-1 are formed in the reactions with secondary amines. Using 2-{¹⁵N} label, it was shown that the aryl group does not migrate in these reactions. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 613–615, March, 1997.