Search results for "Nuclear magnetic resonance spectroscopy"
showing 10 items of 843 documents
Nitramino, NRNO2 (R = H, CH3), as a substituent.13C and15N NMR spectroscopic study of nitraminobenzenes and -pyridines
1993
In order to clarify the special properties of the aryl-bound nitramino substituent NRNO 2 (R=H, CH 3 ), 13 C and 15 N NMR spectra of six nitraminobenzenes and nine nitraminopyridines were measured in DMSO-d 6 and their chemical shifts assigned. 1 H NMr chemical shifts and spin-spin coupling constants of all the compounds were also determined. In contrast to the behaviour of nitropyridines or -benzenes studied previously, most of the present compounds gave very broad 17 O NMR lines even at elevated temperatures and their 17 O NMR data were not useful for any reliable conclusions
Neo-clerodane diterpenoids from Scutellaria lateriflora
1998
Abstract Three new diterpenoids, scutelaterins A-C, have been isolated from Scutellaria lateriflora and their structures established as (11S,13S,16S)-2β,6α,19-triacetoxy-4α,18;11,16;15,16-triepoxy-neo-clerod-14-ene (scutelaterin A), (11S,13S,16S)-6α,19-diacetoxy-2β-(2′-methyl)butyryloxy-4α,18;11,16;15,16-triepoxy-neo-clerod-14-ene (scutelaterin B) and (11S,13S,15R and S)-6α,19-diacetoxy-2β-(2′-methyl)butyryloxy-4α,18;11,16;15,16-triepoxy-neo-clerodan-15-ol (scutelaterin C) by chemical and spectroscopic means. In addition, the already known neo-clerodanes ajugapitin and scutecyprol A were also found in the same source.
Nucleophilic attack within Ge, Sn and Pb complexes containing Me2N(CH2)(3) - as a potential intramolecular donor ligand
1998
Abstract Thirteen tin compounds LxPhySnClz and LPh2SnPhX (x=1–4, y=0–3, z=0–2, XPh, F, Cl, Br, I, OPh), six germanium compounds LxPhyGeClz and four lead compounds LPh2PbPhX (XPh, Cl, Br, I) containing the potential intramolecular donor LMe2N(CH2)3—have been synthesized by Grignard reactions, redistribution, halogenation, exchange of halide and phenylation. Evidence for 1,5-chelation in which the donor Me2N intramolecularly attacks the Lewis-acidic atoms Ge, Sn or Pb is provided by six crystal structure determinations: Me2N(CH2)3SnPh2Cl, 5; Me2N(CH2)3SnPh2Br, 5a; Me2N(CH2)3SnPh2I, 5b; Me2N(CH2)3SnPh2OPh, 5d; Me2N(CH2)3SnPh3·HCl·H2O. 1a; Me2N(CH2)3PbPh2I, 17b), and by solution 13C, 119Sn a…
Über antimon-haltige heterocyclen
1980
Abstract p -Nitrophenyl- and p -tolyl-oxadithia- and trithiastibocanes have been synthesized from the respective aryldichlorostibane and dithiole. The compounds have been characterised by means of 13 C NMR and vibrational spectra (ν(SBS 2 ) 350–320 cm −1 ). The crystal structure of p -nitrophenyltrithiastibocane has been determined ( R = 0.042). The eight-membered ring exhibits a boat-chair conformation. Single-bond distances of SbC and SbS (219, 244 and 245 pm), a 1,5-transannular Sb⋯S interaction (319 pm), and Sb⋯S and Sb⋯O (339 and 353 pm) intermolecular contacts, result in a six-coordinated Sb III (ψ-monocapped octahedral) species. The two additional Sb⋯S distances are in accordance w…
Über polygermane
1986
Abstract The optimum conditions for the synthesis of the trigermanes Ge3Ph8 and Ge3Me2Ph6 according to R2GeCl2 + 2 Ph3GeAk (Ak = Li, K) in HMPT have been determined. The main difficulty is to repress a nucleophilic attack of Ph3Ge− at newly formed GeGe bonds. The mass spectrum of Ge3Me2Ph6 shows rearrangements of the GePh3 and Ph/Me groups. The 13C NMR phenyl signals of di-, tri- and tetra-germanes are nearly identical. Ge3Ph8 and Ge4Ph10 transform to the plastically-crystalline state before melting (ΔH 45.3 and 54.9 kJ mol−1). The crystal structure of Ge3Me2Ph6 has been determined. The molecule has C2 symmetry (GeGe 242.9(1) pm, GeGeGe 120.3(1)°).
Selenium Imides: 77Se NMR Investigations of the SeCl2−tBuNH2 Reaction and X-ray Structures of Se3(NtBu)3, tBuNSe(μ-NtBu)2SO2, and tBuNSe(μ-NtBu)2SeO
2000
The reaction of SeCl2 with tert-butylamine in various molar ratios in THF at −78 °C has been investigated by 77Se NMR spectroscopy. In addition to the known Se−N heterocycles Se6(NtBu)2 (1) and Se9(NtBu)6 (2), the acyclic imidoselenium(II) dichlorides ClSe[N(tBu)Se]nCl (4, n = 1; 5, n = 2) and two new cyclic selenium imides [Se3(NtBu)2]n (3, n = 1 or 2) and Se3(NtBu)3 (6) have been isolated and identified. An X-ray analysis shows that 6 is a six-membered ring in a chair conformation with |d(Se−N)| = 1.833 A. Crystal data: 6, trigonal, P3c1, a = 9.8660(3) A, c = 20.8427(7) A, V = 1757.0(1) A3, Z = 6. The 1H, 13C, and 77Se NMR data for 1−6 are reported, and some reassignments of earlier lite…
Star-shaped conjugated compounds forming nematic discotic systems
2004
Abstract Star-shaped compounds, having a benzene ( 9a,b ) or a 1,3,5-triazine ( 11a,b ) core and stilbenoid arms were prepared. Hexyloxy chains, attached in the middle of the arms, provide nematic discotic phases ND, which are unusual for such systems. The position of the sidechains prevents the micro-segregation, which is valid for star-shaped discs of columnar phases. The stilbenoid character of 9a,b and 11a,b guarantees a high light sensitivity. Apart from the statistical CC bond formation by irradiation in solution or in the LC phases, a topochemically controlled chemo-, regio- and stereoselective photocyclodimerization 11a → 12 was found in the crystalline state. The structure determin…
Application of palladium complexes bearing acyclic amino(hydrazido)carbene ligands as catalysts for copper-free Sonogashira cross-coupling
2015
Abstract Metal-mediated coupling of one isocyanide in cis-[PdCl2(CNR1)2] (R1 = C6H11 (Cy) 1, tBu 2, 2,6-Me2C6H3 (Xyl) 3, 2-Cl-6-MeC6H3 4) and various carbohydrazides R2CONHNH2 [R2 = Ph 5, 4-ClC6H4 6, 3-NO2C6H4 7, 4-NO2C6H4 8, 4-CH3C6H4 9, 3,4-(MeO)2C6H3 10, naphth-1-yl 11, fur-2-yl 12, 4-NO2C6H4CH2 13, Cy 14, 1-(4-fluorophenyl)-5-oxopyrrolidine-3-yl 15, (pyrrolidin-1-yl)C(O) 16, 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propane-1-yl 17, EtNHC(O) 18] or sulfohydrazides R3SO2NHNH2 [R3 = Ph 19, 4-MeC6H4 20] led to a series of (hydrazido)(amino)carbene complexes cis-[PdCl2{ C (NHNHX) N(H)R1}(CNR1)]; X = COR2, SO2R3 (21–48, isolated yields 60–96%). All prepared species were characterized by elemental…
Cytotoxic bufadienolides from the leaves of a medicinal plant Melianthus comosus collected in South Africa.
2020
Abstract From the leaves of South African medicinal plant Melianthus comosus, four previously undescribed bufadienolides, 16β-formyloxymelianthugenin (1), 2β-acetoxymelianthusigenin (2), 2β-hydroxy-3β,5β-di-O-acetylhellebrigenin (3), and 2β-acetoxy-5β-O-acetylhellebrigenin (4) were isolated together with two known bufadienolides. The structural elucidation of the compounds was based on 1D and 2D NMR spectroscopy, high-resolution mass spectrometry, and other spectroscopic methods. The relative configurations were determined by single-crystal X-ray crystallography analysis and NOESY correlations. The isolated compounds displayed strong cytotoxicity against MCF-7 breast cancer cells, sensitive…
Adducts of Tellurium Tetrachloride with Allyl Alcohol and Allyl Acetate: 1,2- vs 1,3-Addition and Structure and Dynamics of Te···O Interactions in D…
2002
The compounds Cl 3 Te[CH 2 CH(Cl)CH 2 O(H)...].Cl 2 Te[-CH 2 CH(Cl)CH 2 O-] (1) and Cl 3 Te-[CH 2 CH(CH 2 Cl)OC(CH 3 )=O...] (2) were prepared by the reaction of TeCl 4 with allyl alcohol and allyl acetate, respectively. Their molecular and crystal structures were investigated by single-crystal X-ray analysis, 1 H- 1 H-NOESY experiments, IR spectroscopy, and ab initio geometry optimization. 1 is a composite compound, whose subunits Cl 2 Te[-CH 2 CH(Cl)-CH 2 O-] (1A) and Cl 3 Te[CH 2 CH(Cl)CH 2 O(H))...] (1B) are linked in the solid state via Te...Cl-Te and O...H-O bridges. Both Te atoms are involved in similar five-membered rings, having a covalent Te-O bond in one case (1A) and a dative Te…