A new strategy involving the use of 2D long-range δC/δH correlation in conjunction with the 1D proton-coupled 13C NMR spectrum has been applied to the structural elucidation of ekeberginine, a new carbazole alkaloid from the stem bark of (Meliaceae). 相似文献
The synthesis and characterisation of the complexes [(p-CH3C6H4NCH(d(OAc)]2 (II) are reported. These complexes react at very different rates with carbon monoxide in methanol to give the ortho-substituted esters, p-CH3C6H4NCHC6H3Y - 2R, R = CO2CH3, with electron withdrawing Y substituents slowing the reaction. The 13C{1H} data for II show a linear correlation of δ(C(2)) in the 5′-complexes (Y trans to PdC) with δ(C(4)) of monosubstituted benzene compounds. For Y = 5′-NO2, 4′-NO2 and 4′-Cl, the bis complex [{p-CH3C6H4NCH( is formed in a secondary reaction. 相似文献
δ13C values and coupling constants (1J(13C1H), 1J(13C13C), nJ(19F13C) are reported for 19 polyfluorinated organic compounds. It is shown that the shielding of carbon depends upon the number of fluorine atoms in α -position. If the RF-group is linked to a π -system hyperconjugative η-π interaction accounts for the δ13C data. The values 1J(13C1H) and 1J(13C13C) are in qualitative agreement with changes of the s-character of the respective bonds. 相似文献
The Raman, and infra-red spectra of Na+, K+, Rb+, Cs+, NH4+, C5H5NH+ and -Bu4N+ salts of the TeF5- ion are reported. They are assigned Cs symmetry. 19F n.m.r. spectra of the -Bu4N+ salt show J(Fax-Feq)50.4Hz, J(19Feq-125Te)1375.7Hz, J(19Fax-125Te)2883.3Hz and J(19Feq-123Te)1143.8Hz. No n.m.r. evidence was found for TeF62-. 相似文献
The 1B1 states of H2O and D2O have been observed by means of three photon absorption (four photon ionisation) spectroscopy. Differences between the experimentally observed 3 + 1 multiphoton ionisation spectrum and that predicted by the appropriate asymmetric-top three-photon line-strength theory are attributed to state predissociation. Two separate predissociation mechanisms have been identified, one (heterogeneous) relying on a-axis parent molecular rotation to couple the bound B1 state to an unbound state of A1 electronic symmetry, the other (homogeneous) involving a second, dissociative excited electronic state of B1 symmetry. Having established the detailed state predissociation dynamics, two photon absorption spectra of H2O and D2O ( ← ) can be predicted accurately: studies of individual quantum-state-selected photofragmentation processes from H2O() are proposed. 相似文献
In the reaction of C5H5Co(CO)(C3F7)I with isonitriles in the molár ratio the brown complexes C5H5Co(CNR)(C3F7)I are formed. The fluorine atoms of the α-CF2 groups are diastereotopic because of the asymmetric center at the Co atom. With (—)-α-phenylethylisonitrile a pair of diastereoisomers is obtained which could not be separated.C5H5Co(CO)(C3F7)I and C5H5Co(CNR)(C3F7)I react with excess isonitrile with the formation of benzene soluble, yellow salts [C5H5Co(CNR)2(C3F7)]+I?, which can be transformed into the corresponding PF?6 salts. The new compounds were characterised by C, H, N, Co analyses, molecular weight determinations, IR, 1H NMR, 19F NMR, 13C NMR, ESCA and mass spectra. 相似文献
The addition of trimethylphosphane to five-membered metallacyclic vinylketone complexes of the type ArR) (I) (Ar = η5-aromatic ring system: C5H5, C5H4Me, C5Me5; R = Me, Et, n-Bu; M = Mo, W) in pentane solution results in the formation of the ylidic metallacyclopropane complexes ArH(COR)] (II). In these 1:1 adducts the three-membered ring is stabilized by an electron-donating phosphonium and an electron-attracting acyl substituent. The negative charge in the ylidic complexes II is localized on the central metal providing it with Lewis base properties. An extraordinary high electron density can be observed on the metal of the derivative C5H5H-(COMe)] (III) which is formed by a 1:2 addition of C5H5W(CO)(C2H2)-(COMe) and PMe3. The metallacyclopropane complexes II and III are characterized by IR, 1H NMR, 13C NMR, 31P NMR and mass spectroscopy. For C5H5H(COMe)], the results of an X-ray structure determination are presented. 相似文献
The changes in 13C chemical shifts for the structural change R2NH → R2NLi have been measured for a series of dialkylamines. These lithiation shifts are largest at the carbon (3.7 – 9.7 ppm) and decrease in the order α > β > γ > δ. The rates of lithium-hydrogen interchange between R2NH and R′2NLi have been determined. The activation energies are large (9 – 17 kcal/mole) and increase as the size of R or R′ increases. The slow exchange permits the direct measurement of acidity differences between pairs of amines using 13C nmr. 相似文献
Linear relations observed between 19F chemical shifts δ and δ in the series 3 or 4-FC6H4SnA3 confirm the validity of the relations established between δ and o° constants of SnA3 groups.This study has been extended to asymetric groups SnA2B and SnABC. 相似文献
The nucleophilic substitution reactions of some simple fluorobenzenes, C6H6?xFx with sodium methanethiolates Na+SR?(R=Et, -Pr, -Bu) have been studied. Some fully substituted products, C6H6?x(SR)x, could be obtained in DMF as solvent with R = Et and -Pr, but not when R = -Bu. All the new products isolated have been characterized by elemental analysis, and NMR (H-1 and F-19), infrared and mass spectroscopy. 相似文献
Reaction of the 16 electron monomer [Co(η5-C5H5)(S2C2{CN}2)] with various tertiary phosphines and phosphites (L) gives readily the 18 electron monomers [Co(η5-C5H5)(S2C2{CN}2)L] which for L = P(OR)3 have J(C55) ca. 6 Hz but J(C55) = 0 for L = PR3. 相似文献
Absolute rate constants are reported for reactions of C2O(3Σ?) under pseudo-first-order decay conditions. C2O is generated by laser photodissociation of C3O2 at 266 nm, and detected by dye-laser induced fluorescence on the 3Πi-3Σ? transition. Rate constants of (433 ± 12), (3.30 ± 0.12) and (1.12 ± 0.05) × 10?13 cm3 molecule?1 s?1 are reported for reactions with NO, O2 and isobutene. The NO value is approximate due to an apparent dark reaction between NO and C3O2. Upper limits of 1 × 10?14 cm3 molecule?1 s?1 are reported for reactions with H2, CO2, C3H2 and C2H4. The C2O + C3O2 reaction does not follow pseudo-first-order decay kinetics. Two explanations are proposed to explain this observation. Results are compared with previous relative rate measurements and are discussed in terms of their relevance to combustion chemistry. 相似文献
A novel C19-diterpenoid alkaloid designated as tatsinine has been isolated from the roots of and its structure (3) has been derived from 1H NMR and 13C NMR spectroscopic evidence. 相似文献
Incorporations of [1-13C]?, [2-13C]?, [1,2-13C2]-acetates and [13C]-methionine into anditomin, a metabolite of , indicate its formation by a mixed polyketide-terpenoid biosynthetic pathway similar to that elucidated for andibenin; observations are made on the possible biosynthetic relationship of the metabolites with austin and terretonin, mycotoxins recently isolated from and respectively. 相似文献
The metal carbonyl anions [Fe(η-C5H5(CO)2]? and [Re(CO)5] undergo regio- and site-specific [2 + 2]-cycloadditions with the ketenimines Ph2CCNR (R = Me, Ph) to give the (isolable) anionic complexes [Ln(O)}]? (LnM = Fe(η-C5H5)CO, Re(CO)4) which have been alkylated and acylated at the exocyclic oxygen atom of the carbonyl function. The result is stable neutral complexes having a metallaazetidine structure which is composed of an α-metallated enamine and an N,O carbene part. IR, 1H, and 13C NMR data are presented. 相似文献
Allylbenzene is isomerized to - and -β-methylstyrene at 35–60°C in the presence of [(C6H5)3P]4Ru(π-CH3CN)·CH3CN. Two hydrido-η3-1-phenylallyl ruthenium complexes have been detected by proton nmr spectroscopy during the reaction and the predominant one of formula [(C6H5)3P]2RuH(η3-C3H4C6H5)(CH3CN) has been isolated. The structure of this intermediate contains cis phosphines, mutually trans hydrido and acetonitrile ligands and the 1-phenylallyl ligand in a -configuration. A similar structure with an -configuration of the 1-phenylallyl ligand is suggested for the other detected intermediate. These complexes indicate that this isomerization is initiated by oxidative-addition of ruthenium(0) to an allylic C-H bond with the formation of distinct η3-allyl metal hydride species as has been proposed in a number of metal catalyzed olefin transformations. 相似文献
The tertiary phosphines R2PF2)n (R = C6H5 or C6H11; n = 2,3, or 4) react with M(CO)6 (M = Cr, Mo, W) to give R2PF2)nM(CO)5 in which the ligand is bonded to M through P alone. Similar bonding is found in some chloro-complexes of platinum and palladium. 相似文献
The known complex, -(η-C5H5)2Rh2(CO)2(CF3C2CF3) is formed in high yield from (η-C5H5)Rh(CO)2 and CF3FCCF3 at 100°. The less stable -isomer of the complex is obtained in low yield from the same reaction. The infrared, 1H, 19F and 13C NMR spectra of the two isomers are compared. The -isomer undergoes CO scrambling in solution at room temperature, and the variable temperature 13C NMR spectra are consistent with a pairwise bridge opening and closing mechanism. The mechanism is extended to account for the isomerization of to isomer, whihc has a half-life of 12 h at room temperature. The 13C spectrum indicates that the -isomer is static in solution at room temperature. The -isomer is reversibly protonated by protonic acids, and BF4? and PF6? salts of the protonated species can be isolated. The spectroscopic properties of these salts are consistent with protonation at one of the alkynyl-carbons, but it is not possible to distinguish between two alternative structures for the complex cation.Treatment of (η-C5H5)2Rh2(CO)2(CF3C2CF3) with (η-C5H5)Rh(CO)2 gives the trinuclear complex (η-C5H5)3Rh3(CO)(CF3C2CF3) in 80% yield. The analogoug but-2-yne complex is formed from (η-C5H5)3Rh3(CO)3 and MeCCMe. The infrared, 1H, 19F and 13C NMR spectra indicate that the hexafluorobut-2-yne complex exists in two different structural arrangements in solution. One has an edge bridging, and the other a face bridging carbonyl. The proportion of the isomers is affected by the solvent polarity. The spectra of the but-2-yne complex indicate it is fluxional at room temperature, and has a face bridging structure in solution regardless of the polarity of the solvent. Reversible protonation of the hexafluorobut-2-yne complex occurs in protonic acids, and the salt [(η-C5H5)3Rh3(CO)(CF3C2CF3)H]+[BF4]?,H2O can be isolated. The spectroscopic properties of this complex are consistent with a structure incorporating an edge-bridging carbonyl, and probably, an edge-bridging hydride ligand. 相似文献
A very unusual dithiokikeptopiperazine structure () has been assigned to aspiroclorine, C9H12N2O5S2Cl, produced as a biologically active substance together with canadensolide by , which has been found to be identical with the antibiotic A 30641 from . 相似文献