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1.
A series of endo- and exo-2-triorganostannylnorbornanes have been synthesized by various methods, some of them leading to pure stereoisomers. The 2-triorganostannylnorbornanes have been characterized by their 13C and 119Sn NMR spectra.  相似文献   

2.
Some monomer model compounds of lignin have been selectively 2H and 13C labelled: vanillin, ethyl ferulate, coniferyl alcohol and ethyl hydrogen malonate. Deuterium isotope effects on the 13C chemical shifts in [formyl-2H]vanillin, [5-2H]vanillin and [α,α,5-2H3]coniferyl alcohol made the unambiguous assignment of the aromatic 13C signals possible. Absolute 1,2,3J(CC) values have been determined on 13C spectra of [formyl-13C]vanillin, and of ethyl ferulate and coniferyl alcohol in which the vinylic C-γ and C-β carbons were 13C enriched. It has been possible to measure 4J(C?O, C-4) in vanillin and 4J(C-γ, C-4) in ethyl ferulate. The determination of 1,2,3,4J (CH) absolute values was done by means of gated decoupled 13C spectra of the non-labelled compounds. When second order effects made the use of this technique impossible we determined certain J(CH) values and their signs either by analysing the 1H NMR spectra of 13C labelled coniferyl alcohol [2J(C-β, H-γ), 2J(C-β, H-α), 2J(C-γ, H-β), 3J(C-γ, H-α)] or by a double irradiation experiment on the 250 MHz 1H NMR spectrum of ethyl [β-13C] ferulate [for 2J(C-β, H-γ)].  相似文献   

3.
The structural elucidation by NMR spectroscopy of trisubstituted α-pyridones and the isomeric 2-amino-γ-pyrones as well as their internal and external pyrylium salts is described. The most useful parameter for the differentiation between α-pyridones and isomeric γ-pyrones is the geminal coupling constant 2J(C-6, H-5) which changes from ~2.5 Hz to ~7 Hz whenever the cyclic amide group is replaced by an oxa-function; this applies to both the γ-pyrones and their pyrylium salts. The value of J(C-6, H-5) in the pyridones resembles that of the analogous coupling in N-vinylacetamide, whose sign determination by the selective population inversion (SPI) technique is reported. The 13C chemical shifts of seven pyridones, pyrones and pyrylium salts are reported and their structural correlations are discussed. Quick structural assignments in these classes of compounds may also be performed by evaluating the 14N chemical shifts, which often are accessible by the {14N}—1H-INDOR technique. The proton coupled 13C NMR spectra of two tetrasubstituted pyridines are also reported, and empirical correlations between long range C? H coupling constants and substituent electronegativity are discussed.  相似文献   

4.
Photoelectron spectra of endo- and exo-cyclopropano-norbornene ( = endo- and exo-tricyclo[3.2.1.02.4]octa-6-ene) show that a significant homoconjugation exists between the π-orbital of the double bond and the symmetric Walsh-es-orbital of the cyclopropane ring in the exo-isomer, whereas the interaction is negligeable in the endo-derivative.  相似文献   

5.
Satellites corresponding to metal-proton coupling constants through two and four bonds are observed in PMR spectra of Pb, Sn and Hg allenic derivatives. The relative signs of these coupling constants are deduced from analysis of the satellite spectra: 2J(X? H) and 4J(X? H) are of opposite signs for X = 207Pb, 119Sn, 117Sn and of same sign for X = 199Hg. Probable absolute signs of reduced coupling constants are discussed in relation to published data: 2K(X? C? H) is probably positive for X = 207Pb, 119Sn, 117Sn and 199Hg. 4K(X? C?C?C? H) is probably negative for X = 207Pb, 119Sn, 117Sn and positive for X = 199Hg.  相似文献   

6.
Diorganotin complexes of monoisopropyl and monomethyl nadiate, succinate, and phthalate were synthesized and characterized by elemental analysis, FT-IR, 1H NMR, 13C NMR, and 119Sn NMR spectroscopic techniques. The spectroscopic investigation demonstrated that carboxylate is bidentate in the diorganotin complexes. On the basis of 1 J(119Sn–13C) and 2 J(119Sn–1H) values, C–Sn–C bond angles were also calculated. The newly synthesized complexes were also screened for their antibacterial activities against Gram-positive and Gram-negative pathogenic strains of bacteria.  相似文献   

7.
The 13C and 119Sn NMR spectra of a set of di-n-butyltin(IV) compounds and their complexes in coordinating and non-coordinating solvents have been studied. The results have shown that it is possible to describe semiquantitatively the shape of coordination polyhedra of these compounds from analysis of their δ(119Sn) and 1J(119Sn-13C) parameters. The values of δ(119Sn) define the regions with different coordination numbers of the central tin atom, so that four-coordinate compounds have δ(119Sn) ranging from about + 200 to −60 ppm, five-coordinate compounds, −90 to −190 ppm, and six-coordinate compounds, −210 to −400 ppm. The values of 1J(119Sn-13C) were used for the calculation of the CSnC angle in the coordination polyhedron of individual compounds.  相似文献   

8.
In 2-trifluoromethylphenyldifluorophosphine the proximate couplings 4J(19F31P) and 5J(19F19F) are + 68.3 and + 8.3 Hz, respectively. 1J(13C31P) is ?57.0 Hz, 2J(13C-1, 10F) is + 9.9 Hz and 2J(13C-6, 13C-6, 31P) is + 10.1 Hz. The trifluoromethyl substituent induces substantial changes in some coupling constants, particularly those between the 31P and ring 13C nuclei.  相似文献   

9.
The 13C n.m.r. spectra of 18 derivatives of the tricyclo[3.2.1.02,4]octanes have been determined. This series includes methyl, hydroxyl and oxo substituted examples to compare the effects of these substituents on the skeletal carbon shieldings with those observed for the corresponding norbornanes and bicyclo[3.2.1]octanes. In general, the trends are similar and the perturbations associated with closely neighboring groups follow a consistent pattern. The shielding data for the exoexo and exoendo isomers of tetracyclo[3.3.1.02,406,8]nonane are also reported.  相似文献   

10.
The 13C and 119Sn NMR spectra of some tribenzyltin(IV) compounds and their complexes in coordinating and non-coordinating solvents have been studied. The δ(119Sn) chemical shifts and coupling constants 1J(119Sn, 13C) clearly depend on the coordination number of the central tin atom and the geometry of its coordination polyhedra. Approximate ranges of the characteristic values of both the NMR parameters were determined for various configurational types of tribenzyltin compound. The 13C and 119Sn NMR parameters found are indicative of a distinct interaction between the polarized σ(SnC) bond and adjacent π-electron system of the aromatic ring(s).  相似文献   

11.
Reactions of p-nitrophenyloxirane with amines containing fragments with bicyclic skeleton of norbornene, norbornane, epoxynorbornane (stereoisomeric exo- and endo-5-aminomethylbicyclo[2.2.1]hept-2-enes, N-benzyl-endo-5-aminomethylbicyclo[2.2.1]hept-2-ene, endo-5-(2-aminoethyl)bicyclo[2.2.1]hept-2-ene, stereoisomeric exo- and endo-2-aminomethylbicyclo[2.2.1]heptanes, 2-(1-aminoethyl)bicyclo[2.2.1]heptane, exo-5-aminomethyl-exo-2,3-epoxybicyclo[2.2.1]heptane) were investigated. The aminolysis of p-nitrophenyloxirane occurred regioselectively according to Krasusky rule as was proved by 1H and 13C NMR data. As shown by 1H and 13C NMR spectroscopy the oxyalkylation product obtained from N-benzyl-endo-5-aminomethylbicyclo[2.2.1]hept-2-ene was composed of two diastereomers originating from the presence of a chiral nitrogen atom in the rear part of the rigid bicyclic skeleton. New products of amino groups transformation in the molecules of hydroxyamines were obtained by reaction with p-methylbenzoyl chloride and p-nitrophenylsulfonyl chloride. Regioselectivity of the attack of electrophilic reagents on the nitrogen in the hydroxyamines was confirmed by IR and 1H NMR spectra of the products. The data on pharmacological activity tests of N-2-hydroxyethyl(p-nitrophenyl)-5-aminomethylbicyclo[2.2.1]hept-2-ene are reported.  相似文献   

12.
The complexes [Rh(X)(H)(SnPh3)(PPh3)(L)] (X = NCBPh3 (a), N(CN)2 (b), NCS (c), NCO (d), N3 (e); L = 1‐methylimidazole) ( 1 ) show systematic changes in δ(119Sn), δ(103Rh), J(119Sn–1H) and J(119Sn–103Rh) that are related to the electron‐donating properties of X. As X becomes more electron‐rich, δ(103Rh), J(119Sn–1H) and J(119Sn–103Rh) increase and δ119Sn) decreases. The related complexes trans‐[Rh(X)(H)(SnPh3)(PPh3)2(L)] (X = N(CN)2, NCO; L = 4‐carboxymethylpyridine (x), pyridine (y) and 4‐dimethylaminopyridine (z)) ( 2 ), show a continuation of the trends in δ(119Sn) and J(119Sn–1H), but not δ(103Rh) or J(119Sn–103Rh). Data for 1 and 2 show that within certain limits of type of ligand varied (X = N‐donor, L = a pyridine) and coordination geometry, the response of δ(119Sn) and J(119Sn–1H) to changes in electron density on rhodium is largely independent of the means by which the change is effected.Copyright © 2001 John Wiley & Sons, Ltd.  相似文献   

13.
The solution conformation of L-6-methylperhydroimidazo[1,5-c]thiazole-5,7-dione (γ-thiaprolinehydantoin) has been determined from an extensive 1H and 13C NMR study, allowing the extraction of vicinal inter-proton and carbon-hydrogen coupling constants. The major conformation of the thiazolidine ring is an envelope with C-δ as the flap exo?). In solution the preferred solid state (twist) conformer with C-α exo and C-β endo (αβT) is only a minor contributor. 13C spin–lattice relaxation data reveal the flexibility of the thiazolidine ring.  相似文献   

14.
The absolute configurations of nine 2,3-O-benzylidene-α-L-rhamno- and α-D-mannopyranoside diasteteomeric pairs were determined and the 13C NMR spectra of further thirteen α-L-rhamno- and α-D-mannopyranosides, having various substituents, were completely assigned.Four 13C shifts were found suitable for the determination of the absolute configuration of the dioxolane skeleton. (1) The chemical shift of the acetal carbon in the endo isomers is between 103.9 and 104.7 ppm whereas for the exo isomers this region extends from 102.8 to 103.4 ppm; (2) The formation of the dioxolane ring causes a deshielding effect for the bridgehead carbons, in the exo isomers this effect is more pronounced for C-3 whereas in the endo isomers for C-2. For C-4, shielding effect was found in the exo isomers and deshielding effect in the endo ones; (3) The chemical shift of the quaternary carbon of the phenyl group is greater in the exo isomers than in the endo ones; (4) The difference between the shift of the acetal carbon and that of the quaternary carbon of the phenyl group in the exo isomers is greater than 35.4 ppm, in the endo isomers is less than 33.7 ppm.  相似文献   

15.
77Se n.m.r. spectra of twenty-six organoselenium compounds, including some with an endocyclic selenium atom, have been recorded. Our measurements complete the scale of chemical shifts previously established by McFarlane. It seems difficult to define a range of chemical shifts which is characteristic of the valency state of selenium or of its endo- or exocyclic position. Some results are discussed qualitatively. In the case of selenolo[2,3-b]thiophene, evidence has been obtained for a 4J[Se, H] coupling across the sulphur atom.  相似文献   

16.
The synthesis and 119Sn NMR characteristics of new five-coordinate tris(trichlorostannato) complexes of RhI, IrI and PtII are reported. The RhI and IrI complexes are complex dianions of the form (PPN)2[M(SnCl3)3L2] where L can be CO, CN (cyclohexyl) or L2, a diolefin such as 1,5-COD or NBD (norbornadiene). The anionic platinum complexes (PPN)[Pt(SnCl3)3L2] contain similar L ligands. A number of neutral monotrichlorostannato complexes of type [M(SnCl3)L4] including [Ir(SnCl3)(NBD)(1,5-COD)] have been prepared and characterized. Their δ(119Sn), δ(13C), δ(195Pt) as well as 1J(103Rh, 119Sn), 1J(195Pt, 119Sn), 2J(119Sn, 117Sn) and 2J(119Sn, 13C) data are given. A trans influence series, based on 1J(195Pt, 119Sn), reveals the following sequence: H? > PR3 > AsR3 > SnCl3? > olefin > Cl?.  相似文献   

17.
Structural correlations have been carried out from 13C chemical shifts (δ) and by analysis of 1J(CH) coupling constants, and the conformation about the glycosidic bond has been studied by means of the 3J(CH) vicinal coupling constants between C-8 and H-1′ of some adenine nucleosides such as adenosine (Ado), N(7)-β-D-ribofuranosyladenine (N(7)-Ado), N(9)- and N(7)-β-D-xylofuranosyladenine (N(9)-xylAde and N(7)-xylAde), N(9)-(3-chloro-3-deoxy-β-D-xylofuranosyl)adenine (3′-Cl-xylAde) and N(9)-(2-chloro-2-deoxy-β-D-arabinofuranosyl)adenine (2′-Cl-araAde). The analysis of the influence on δ13C of the nature and configuration of the substituent in the carbohydrate fragment of the molecule has revealed two types of effects, namely, 1,2-cis and 1,2-trans. This approach, as well as the 3J(CH) values and the analysis of the C-3′-endo?C-2′-endo equilibrium of the carbohydrate fragment of nucleosides, and circular dichroism (CD) data, provides important information on the conformation about the glycosidic bond. The magnitudes of 3J(C-4, H) are indicative of the position of attachment of the carbohydrate fragment to the heterocyclic base.  相似文献   

18.
The 1H NMR spectra of 2-exo-hydroxymethyl-3-endo-methylnorbornene and the corresponding 2-endo-3-exo isomer have been completely assigned with the aid of lanthanide reagents. This enabled a full analysis of the unusual spectrum of 2-exo-hydroxy-methyl-3-endo-methylnorbornene to be undertaken, confirming the proposed structure. The ΔEu values for 2-exo-hydroxymethyl-3-endo-methylnorbornene and the 2-endo-3-exo-isomer have been used to test the effect of rotational averaging on the calculated pseudo contact shifts. Good agreement is obtained for a dynamic model in which the Eu atom exchanges between two sites on the oxygen atom of the OH bond, and in which the rotational equilibrium about the CH? CH2OH bond is explicitly considered.  相似文献   

19.
Carbon-13, proton coupling constants have been measured in eighteen different 2-substituted propanes. 1J(C-2,H) shows variations similar to those observed previously for monosubstituted methanes. 2J(C-2,H) is essentially independent of the substituent at C-2, while 2J(C-1,H) varies over a range of at least 5 Hz. The latter coupling constant becomes more positive as the electronegativity of the substituent increases while 3J(CH) decreases as the electronegativity of the substituent increases. The observed trends in nJ(CH) are compared with those calculated using semi-empirical molecular orbital theory at the INDO level of approximation.  相似文献   

20.
The 13C NMR spectra of a series of epoxides derived from endo- and exo-dicyclopentadiene and their partially hydrogenated compounds were determined to examine the substituent effects arising from the introduction of the oxirane ring in comparison with those found in other ring systems. The 13C signals of some epoxides were assigned by using lanthanide shift reagents. Characteristic substituent effects exerted by an oxirane ring were demonstrated. Marked steric γ-effects of ?8—13 ppm were observed at the bridge carbon signal in the bicyclo[2.2.1]heptane skeleton. Differences were found in the substituent effects between endo- and exo-dicyclopentadiene epoxides, and have been discussed in relation to the molecular geometry.  相似文献   

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