The novel indolosesquiterpenes isopolyalthenol 3 and neopolyalthenol 4 have been obtained from Polyalthia suaveolens (Annonaceae). A pathway for the biogenesis of indolosesquiterpenes is considered. 相似文献
Preparations of new benzylic organotin compounds are presented. 119Sn NMR studies show long range coupling constants 119Sn119Sn and intramolecular coordination of tin. 相似文献
Heterogeneous reaction of TRIS 1 with nitro-aldehydes leads to oxazolidines in good yield. New products are obtained as monocyclic or bicyclic compounds, and are of potential medicinal value. 相似文献
CsTeF5 was synthetized in hydrofluorhydric solution by action of CsF and TeO2. The structure was solved by means of three dimensional Patterson synthesis (final Rw value = 0,033). This structure contains isolated TeF5 groups which are distorted square pyramids (Cs symmetry). The apical Te-F bond distance and the basal Te-F bond distances are 1,81 , 1,91 and 1,95 Å respectivly. 相似文献
In the presence of dichlorobis(triphenylphosphine) nickel, acetylenic compounds undergo stereospecific or stereoselective syn addition of non recuding Grignard reagent. With reducing Grignard reagents, addition and reduction reactions are observed. These reactions yield vinylic organomagnesium compounds. A catalytic process is proposed to explain the experimental results. 相似文献
The synthesis of two new dihydroxy phenacylidene triphenylphosphoranes from 2,4-dibenzoyloxy and 2,5-dibenzoyloxy acetophenones is described. By acylation of the hydroxyl groups of theses ylids, intramolecular of the esters carbonyl group and hydrolysis of the second esters group, some 6-hydroxy and 7-hydroxy chromones are prepared with good yields. 相似文献
CsSbClF3 was prepared in aqueous solution with CsCl and SbF3. The structure was solved by means of a three dimensional Patterson synthesis. Antimony shows an unpublished coordination 8 : 5 fluorine atoms, 2 chlorine atoms and the lone pair of electrons E situated on the corners of a hendecaedron 相似文献
Carbon-13 chemical shifts, spin-lattice relaxation times and nuclear Overhauser enhancement factors at 28°C are reported for a series of polyfluoroaliphatic compounds : , and perfluoroalkyl nonionic surfactants CmF2m+1CH2(OC2H4)nOH with m = 6, 7 and n = 3, 4, 5, 6 and C6F13CH2CH2CONH(C2H4O)nH with n = 3, 4. The influence of the perfluoroalkyl group on the 13C chemtcal shifts of the neighbouring hydrogenated carbons is discussed in terms of hyperconjugative type interactions between lone electron pairs on fluorine and the neighbouring CC or CO bond. Relaxation data show similar flexibilities of the fluorinated chains in the different molecules investigated. Nonionic surfactants exhibit segmental motions in both the hydrophobic perfluoroalkyl and the hydrophilic polyoxyethylene chains ; these motions appear to be similar to those of the analogous hydrogenated surfactants. 相似文献
Organomercuric compounds of the general formula and [RCOCH(R′)]2Hg, obtained from three ketones, 2,2-dimethyl 3-pentanone, 1-mesityl 1-propanone and 1-mesityl 1-ethanone, have been studied by 13C and 199Hg NMR techniques. Coupling constants J(CHg) and J(HgH) are consistent with C-metalated species; in each case the values of δ(C(2)) and J(C(2)H) observed are higher than expected for purely sp3 carbon. The contribution of O-metalated species and hyperconjugative effects are discussed. For two dioxomercuric compounds (R′ Me, R t-Bu, mesityl) the existence of diastereoisomers is suggested from 199Hg NMR data. 相似文献
Optimized geometries and conformational analysis of P(t-Bu)2F and P(t-Bu)2H molecules are investigated within the framework of the CNDO/2 approximation. The CPC angles are found to be equal to 114° in agreement with the 113°8 value provided by X-ray study of the trans-NiBr2 [P(t-Bu)2F]2 square planar complex. Therefore, it seems that the highest XPX value in the PX3 series is observed for di-tert-butyl derivatives and not for the tri-tert-butylphosphine. 相似文献
The compounds AlX3-2CH3CN and AlX3-1.66CH3CN (X = Cl, Br) are prepared in order to study the vibrational properties of AlX(CH3CN)2+5. The different chemical phases obtained are characterised by X-ray diffraction. It is shown that AlCl3-2CH3CN and AlBr3-2CH3CN are isomorphic and unit cell parameters are determined. The spectra of the cations AlX(CH3CN)2+5 in the 600-50cm?1 range are interpreted by comparison with those of Al(CH3CN)3+6 and from the data obtained from H-D substitution. Analysis of the spectra of the complexes AlX3-1,66CH3CN enables the formula [2AlX?4: AlX(CH3CN)|2+5] to be postulated. 相似文献
The structures of the two new ferrites BaLa2Fe2O7 and SrTb2Fe2O7 with tetragonal symmetry have been resolved by X-ray and neutron diffraction performed on powder samples. In both compounds the arrangement of atoms present a close resemblance with the idealized Sr3Ti2O7 structure. It consists of a packing along the c axis of two different blocks. One is formed by the adjunction of two perovskite cells and the other one by a halved rocksalt Sr(Ba)O cell. The iron cation lattice is built by infinite double layers perpendicular to the c axis with the shortest Fe3+Fe3+ distances inside the double layers much shorter than between the layers. In BaLa2Fe2O7, Ba2+ is located on a regular 12-coordinated site and La3+ in a regular 9-coordinated polyhedron. Fe3+ is surrounded by five oxygen neighbours at 1.98 Å, building a rather regular tetragonal pyramid, with a sixth oxygen at 2.25 Å. In SrTb2Fe2O7, Sr has only eight close neighbours at ~2.80 Å and four more distant at 3.15 Å. Tb3+ has seven close neighbours, six building a distorted octahedron with the largest triangular face capped by the seventh oxygen. Fe3+ again has five neighbours, but due to the lowering of the symmetry, the square pyramid has become a distorted trigonal bipyramid. 相似文献
The trioxotetrafluoroditelluric (IV) acid, H2Te2O3F4, was synthetized in fluorhydric solution and characterized by X-ray powder diffraction. The structure was solved by means of three-dimensional Patterson synthesis (final R value = 0,026). This structure is characterized by Te2O3F4 groups linked by hydrogen bonds to form a very distorted diamond network. 相似文献
The Raman and infrared spectra (4000200 cm?1) of (C4H4P)Mn(CO)3 and (C4D4P)Mn(CO)3, and of [C4H2(CH3)2P]Mn(CO)3 and [C4D2(CH3)2P]Mn(CO)3 in the liquid and solid states (10–400 K) have been investigated. A complete vibrational assignment is proposed and valence force fields of the (C5H5) and (C4H4P) cycles are compared. From these results, it is clearly shown that the (C4H4P) rings are more electrophilic and weaker π-electron donors than (C5H5) rings, this is in agreement with their chemical behavior. 相似文献
The crystal and molecular structures of acetato(2-phenylazophenyl-C,N′)tellurium(II) (I) and (2-phenylazophenyl-C,N′)thiocyanatotellurium(II) (II) have been determined. The structure of the former consists of discrete molecules in which weak intramolecular Te?ctdot;O [2.953(4) Å] interactions occur. However, the structure of the latter compound shows a very weak intermolecular Te?ctdot;N [3.535(3) Å] interaction, which links the molecules into dimers. The coordination about tellurium can be considered as approximately trigonal bipyramidal with the carbon atom and the two lone pairs in the equatorial positions and either N and O(I) or N and S (II) in the axial positions. 相似文献
The Diels-Alder reactivity of two captodative olefins, 2-morpho-lino-acrylonitrile and 2-(N-methlanilino) -acrylonitrile , towards four conjugated dienes is evaluated.In every cases, isomeric {4+2} cyclo-adducts are obtained.With olefin yields are better than with olefin . The adducts are easily transformed in to the corresponding ketones by a mild hydrolysis of the α-aminonitrile group. Thus, the 1-cyanoenamines can be considered as good ketene equivalents very useful for the synthesis of unsaturated cyclohexanones. 相似文献
Single-phase 1:2 B-site ordered perovskites are formed in the (1−x)A2+(Li1/4Nb3/4)O3-(x)A2+(Li2/5W3/5)O3 systems, A2+=Sr and Ca, within the range 0.238?x?0.333. The X-ray and electron diffraction patterns are consistent with a P21/c monoclinic supercell, , , , β≈125°, where the 1:2 order is combined with b−b−c+ octahedral tilting. Rietveld refinements of the ordered A(BI1/3BII2/3)O3 structures give a good fit to a model with BI occupied by Li and Nb, BII by W and Nb, and a general stoichiometry (Sr,Ca)(Li3/4+y/2Nb1/4−y/2)1/3(Nb1−yWy)2/3O3, y=0.9x=0.21-0.30. The Sr system also includes regions of stability of a 1:3 ordered phase for 0.0?x?0.111, and a 1:1 ordered double perovskite for 0.833?x?1.0. The formation of the non-stoichiometric 1:2 ordered phases is associated with the large site charge/size differences that can be accessed in these systems, and restricted by local charge imbalances at the A-sites for W-rich compositions. These concepts are used to generate stability maps to rationalize the formation of the known 1:2 ordered oxide perovskites. 相似文献