共查询到20条相似文献,搜索用时 15 毫秒
1.
Ajay K. Bose H. Fujiwara Vinayak S. Kamat Girish K. Trivedi Sasanka C. Bhattacharyya 《Tetrahedron》1979,35(1):13-16
13C NMR spectra of some naturally occurring furocoumarins and derivatives have been examined. The assignment of chemical shifts for all the C atoms has been achieved by using techniques recently reported by Bose et al. 相似文献
2.
13C NMR spectra of menthol stereoisomers have been determined. The correlations of chemical shifts of these ring carbons with those of stereoisomeric 2-isopropylcyclohexanols are examined. Observed chemical shifts of 1-Me carbons are compared with those predicted from the chemical shifts of stereoisomeric 1-methyl-4-t-butylcyclohexanes. 13C NMR spectra of menthyl acetates, and cis and trans p -menthanes have also been examined. 相似文献
3.
13CNMR spectra of eight pterocarpans are reported Assignments are based on multiplicities and second-order features in off-resonance decoupled spectra and on chemical shifts in model compounds. Comparison of the degree of long-range (C, H) coupling in 1H-coupled spectra is found useful 相似文献
4.
The results are given of a study of the13C NMR spectra of (–)-3(R)-decursinol, obtusifol, bergapten, isoimperatorin, and oxypeucedanin and its hydrate. The possibility has been shown of using the principle of additive contributions in the assignment of the signals of the carbon atoms in the compounds under investigation.Institute of Toxicology, Ministry of Health of the USSR, Leningrad. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 301–307, May–June, 1982. 相似文献
5.
Fourier 13C and proton NMR spectra of cyanopropyne partially oriented by a nematic phase have been recorded and interpreted. It is shown that more accurate measurements are obtained much more rapidly by observing 13C satellites by Fourier PMR than by direct observation of the 13C spectrum. The geometry has been extracted from direct couplings; a small but systematic discrepancy with microwave spectroscopy is observed for the carboncarbon bond lengths. 相似文献
6.
A. D. Vdovin É. Kh. Batirov A. D. Matkarimov M. R. Yagudaev V. M. Malikov 《Chemistry of Natural Compounds》1988,23(6):660-662
Coumaris ofHaplophyllum obtusifolium Ledeb. — obtusinin, capensin, and fraxetin 7-O--D-glucopyranoside — have been investigated by13C NMR spectroscopy. Several distinctive features of their NMR spectra have been observed. A complete assignment of the13C NMR spectra of these coumarins has been made and their structures have been confirmed.Institute of the Chemistry of Plant Substances, Uzbek SSR Academy of Sciences, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 6, pp. 796–799, November–December, 1987. 相似文献
7.
8.
O. A. Subbotin P. I. Zakharov V. A. Zagorevskii D. A. Zykov 《Chemistry of Natural Compounds》1976,11(4):476-479
Summary The positions of the signals from the C3, C5, C6, and C7 carbon atoms in the13C NMR spectrum of coumarin have been established with the aid of information obtained from the13C NMR spectra of [3-D]-, [4-D]-, and 7-methoxycoumarins and by the use of an additive calculation based on the increments of the methoxy group in the13C NMR spectrum of anisole.M. V. Lomonosov Moscow State University Scientific-Research Institute of Pharmacology, Academy of Medical Sciences of the USSR. Translated from Khimiya Prirodnykh Soedinenii, No. 4, pp. 458–462, July–August, 1975. 相似文献
9.
The 13C NMR spectral parameters of eleven cyclopentenpoliols are discussed. Chemical shift criteria to distinguish isomeric 3' and 4' monodeoxy eucommiols have been clearly established. 相似文献
10.
Silver tetrafluoroborate reacts with Cl(bipy)(CO)2(η3-C3H5)Mo in CH2Cl2 to give the dimeric cation, (μ-Cl)[(bipy)(CO)2(η3-C3H5)Mo]2+, isolated as the crystalline BF4? salt with CH2Cl2 of solvation (5). Complex 5 crystallizes in the triclinic system (space group P, No. 2) with cell parameters: a 11.831(2), b 10.142(3), c 15.618(3) Å; α 93.96(2), β 104.33(2), γ 91.41(2)°, V 1809.5(8) Å3Z = 2, ?calc 1.60 g cm?3. Full matrix refinement with all but three atoms anisotropic converged at R1 = 0.057 and R2 = 0.073 based on 3742 reflections with I > 30(1). The two halves of the dimer are connected by a single chloride bridge (Mo-Cl 2.554(3), 2.519(3) Å, Mo-Cl-Mo 134.0(1)°). The η3-allyl group is oriented so that its open face points toward the two cis-carbonyl groups, a feature common to all L2X(CO)2Mo(η3-allyl) structures determined to date. A molecular orbital analysis shows that this rotational preference of the allyl group has its roots in the strong π-bonding character of the carbonyls. The MO analysis also provides a rationale for regioselectivity observed in the reactions of various η3-allyl complexes with nucleophiles. In particular, the factors which determine whether the terminal carbons are attacked (giving olefin) or whether the central carbon is attacked (giving a metallacyclobutane) are exposed. 相似文献
11.
L. M. Khalilov A. A. Panasenko G. G. Balezina F. A. Selimov U. M. Dzhemilev G. A. Tolstikov 《Chemistry of Natural Compounds》1988,24(3):376-380
The1H and13C NMR spectra of diols of the hexachlorobicycloheptene and-heptadiene series, and also of the diacetates and sulfites corresponding to them, have been investigated. Criteria for the stereochemical assignment of the compounds mentioned on the basis of chemical shifts and spin-spin coupling constants have been determined.Institute of Chemistry, Bashkir Branch, USSR Academy of Sciences, Ufa. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 439–443, May–June, 1988. 相似文献
12.
29Si, 13C and 1H NMR spectra are reported for the series of linear permethylpolysilanes Me(SiMe2)nMe where n = 1 to 6, for the cyclic permethylpolysilanes (Me2Si)n where n = 5 to 8, and for a few related compounds. For linear polysilanes the 29Si and 13C chemical shifts can be accurately calculated from simple additivity relationships based on the number of silicon atoms in α, β, γ and δ positions. Adjacent (α) silicon atoms lead to upfield shifts in the 29Si and 13C resonances, whereas more remote silicon atoms lead to downfield shifts. The 29Si chemical shifts of the polysilane chains are linearly related to the 13C shifts of the carbon atoms attached to the silicon. The 29Si and 13C resonances of the cyclic silanes deviate from this relationship. Ring current effects arising from σ delocalization are suggested as an explanation for the deviations. Proton-coupled 29Si NMR spectra are reported for Me3SiSiMe3 and for (Me2Si)n, n = 5 to 7. 相似文献
13.
The 13C NMR spectra of η3-allylmanganese tetracarbonyl complexes are consistent with an overall Cs, symmetry and involving a σv plane in the Mn(CO)4 fragment. A dynamic carbonyl interchange process was looked for but the results are inconclusive, however the barrier for this process is certainly greater than 42 kJ/mol. This observation suggests an octahedral type geometry rather than a square pyramid type configuration. 相似文献
14.
Bernhard E. Reichert 《Journal of organometallic chemistry》1974,72(2):305-308
The 13C NMR spectra of some methylplatinum(IV) Schiff-base and related complexes have been recorded. The results are interpreted in terms of the differing effects of various donor atoms on a platinumcarbon bond in the trans position. 相似文献
15.
1H, 13C and 29Si NMR spectra of the allylchlorosilanes (CH2CH-CH2-)xSiCl4?x and of triallylbromosilane have been analysed. Results are discussed in terms of inductive and steric effects and of contributions of diamagnetic anisotropy. There is no conclusive evidence for (p-d)π conjugation. 相似文献
16.
Summary The total assignment of the 1H and 13C NMR spectra of the necines of toxic pyrrolizidine alkaloids (retronecine, heliotridine, crotanecine, otonecine), their hydrochlorides and their N-oxides has been performed. The characteristic chemical shift differences between retronecine and heliotridine, as well as the protonation and N-oxidation shift effects in NMR studies of necines at the corresponding position are proposed to be an additional assignment aid. The assignment of the spectra was achieved by the concerted use of 2D correlation spectroscopy.Dedicated to Prof. Dr. Dr. Dres. h. c. Herbert Oelschläger, Frankfurt/Main, on the occasion of his 70th birthday 相似文献
17.
13C NMR data of licodione and its methylated derivatives in keto-enol tautomeric mixture are given, and evidence for correct assignment of α-proton and methyl signals in 1H NMR is presented. 相似文献
18.
Several π-excessive heteropolyaromatic compounds, which contain furan and thiophen ring and are possible antifungal agents, have been synthesized in good yields according to two general methods. The first method has been used to prepare compounds possessing thiophens linked by their 2- and 5-positions, such as the ter-aryls , and . Two precursors of these compounds have been obtained either by the Glaser reaction, or using a novel Pd-mediated reaction. The second method,which consists of the Ni-or Pd-catalyzed heteroarylation of heteroarene halides via cross-coupling with heteroaryl Grignard reagents or zinc halides,has been used to prepare the bi-aryls , which contain two heteroaromatic units, and the ter-aryl . Compound has been also prepared starting from 2-(2-thienyl) furan () by selective lithiation, followed by bromination.The 13C NMR signals of and have been assigned on the basis of the literature data and by relaxation measurements. Relaxation data have been also used to obtain qualitative informations on the conformational equilibria of the bi-aryls , and the ter-aryls . 相似文献
19.
Takehiko Terao Shiro Maeda Tokio Yamabe Kazuo Akagi Hideki Shirakawa 《Chemical physics letters》1984,103(5):347-351
13C NMR spectra of undoped polyacetylene,(CH)x, have been measured. The existence of 3.4 mol% methylene moieties as defects in the (CH)x chains has been observed in trans-(CH)x. Measurements of partially cis-to-trans isomerized (CH)x suggest the existence of isolated cis regions. 相似文献
20.
In connection with structure studies on dammarane type triterpenes and their glycosides, assignments of 13C NMR signals of fifteen 20-hydroxy-dammarane derivatives including Ginseng sapogenins have been achieved by the aid of shift reagents and deuterated compounds. It has been found that the differences of the 17 C, 21 C and 22 C chemical shifts between pairs of C-20 epimers are remarkable especially in the case of 12β-hydroxy derivatives, being significant for the study of the C-20 stereochemistry. 相似文献