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R. A. Kadyrov R. P. Arshinova V. V. Klochkov A. V. Aganov B. A. Arbuzov 《Russian Chemical Bulletin》1985,34(4):724-728
Conclusions In conformity with the data of1H NMR, DM, and the Kerr effect for 2-dialkylamino-2-oxo(thiono, seleno)-1,3,2-dioxaphosphepines, a conformational equilibrium of two forms of twist and chair with an equatorial dialkylamino group is observed in solutions. The equilibrium is displaced in favor of the latter.Then the products were crystallized after removing a part of the solvent in vacuo.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 4, pp. 799–803, April, 1985. 相似文献
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G. Lucente F. Pinnen G. Zanotti S. Cerrini W. Fedeli E. Gavuzzo 《Tetrahedron letters》1981,22(37):3671-3674
Properties, spectral data and X-ray crystallographic analysis of a tetracyclic tripeptidic aza-cyclol, obtained by cyclization of CF3COOH·Pro-Phe-Pro-CNp in aqueous medium, are reported. 相似文献
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R. A. Kadyrov I. Kh. Shakirov R. P. Arshinova S. G. Gnevashev R. R. Shagidullin B. A. Arbuzov 《Russian Chemical Bulletin》1989,38(5):964-971
1. | On the basis of IR and Raman vibrational spectra,1H NMR spectra, and measurements of dipole moments of 4,7-dihydro-2-aroxy-1,3,2-dioxaphosphepines, their 5,6-dichloro analogs are conformationally homogeneous and have a flexible T conformation with anti orientation of the phenoxyl radical. 5,6-Benzo-2-phenoxy-1,3,2-dioxaphosphepine is characterized by a three-component equilibrium in which both chair conformations and the twist conformation participate, with predominance of the first two. |
2. | In phenoxy-substituted 1,3,2-dioxaphosphepines, the plane of the benzene ring is nearly orthogonal to the plane of the . |
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Skowronska A Kowara J Kaminski R Bujacz G Wieczorek MW 《The Journal of organic chemistry》2000,65(2):304-315
A series of new unstable tris(bidentate) hexacoordinated phosphorus compounds 1 with 1,3,2-dioxaphosphorinane rings was prepared and studied by NMR and X-ray crystallography. The X-ray crystal structures showed that the 1,3,2-dioxaphosphorinane ring adopts different conformations depending on the number and size of substituents at the carbon atom C14. Substituents are deployed around the phosphorus atom in a slightly deformed octahedral structure. Deviations in bond lengths around the phosphorus atom depend on the character of the bonds and the distribution of the negative charge. (1)H and (13)C NMR measurements showed that in solution the flexibility of 1,3,2-dioxaphosphorinane ring depends on the size of substituents at the carbon C14. 相似文献
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I. A. Litvinov O. N. Kataeva V. A. Naumov R. P. Arshinova 《Journal of Structural Chemistry》1994,35(1):131-133
A. E. Arbuzov Institute of Organic and Physical Chemistry, Kazan Scientific Center, Russian Academy of Sciences. Translated
fromZhurnal Strukturnoi Khimii, Vol. 35, No. 1, pp. 143–146, January–February, 1994. 相似文献
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Nemykin VN Maskaev AV Geraskina MR Yusubov MS Zhdankin VV 《Inorganic chemistry》2011,50(21):11263-11272
A series of heterocyclic compounds containing trivalent iodine, oxygen, and boron in a five-membered ring were prepared and structurally investigated by X-ray crystallography. 1-Chloro-4-fluoro-1H-1λ(3)-benzo[d][1,2,3]iodoxoborol-3-ol was synthesized by chlorination of 2-fluoro-6-iodophenylboronic acid followed by treatment of the intermediate iododichloride with water. 1-Acetoxy-4-fluoro-1H-1λ(3)-benzo[d][1,2,3]iodoxoborol-3-ol, 1-acetoxy-1H-1λ(3)-benzo[d][1,2,3]iodoxoborol-3-ol, and similar 1-substituted trifluoroacetate derivatives of benziodoxaborole were prepared the hypochlorite oxidation of 2-fluoro-6-iodophenylboronic acid or 2-iodophenylboronic acid in acetic or trifluoroacetic acid, respectively. 1-Acetoxy substituted benziodoxaborole can be further converted to the respective trifluoroacetate by treatment with trifluoroacetic acid or to the 1-hydroxy derivative by basic hydrolysis with aqueous NaHCO(3). X-ray structural studies of 1-chloro- and 1-trifluoroacetoxy substituted benziodoxaboroles 13, 17, and 18 have shown the presence of a planar five-membered heterocyclic ring with unusually short endocyclic I-O bond distance of 2.04-2.09 ?. Slow crystallization of 4-fluoro-1-trifluoroacetoxy-1H-1λ(3)-benzo[d][1,2,3]iodoxoborol-3-ol from methanol resulted in the formation of a tetrameric macrocyclic structure 21 resulting from self-assembly of the initially formed 4-fluoro-1,3-dimethoxy-1H-1λ(3)-benzo[d][1,2,3]iodoxoborol. Structural parameters of the five-membered iodoxoborol ring, such as the planar geometry and the short B-O and O-I bonds lengths in 13, 17, and 18 compared to those in 21 and known benziodoxoles are indicative of partially aromatic character of this ring. Density functional theory (DFT) predicted NIST (0) and NIST (1) indexes for 1-chloro- and 1-trifluoroacetoxy substituted benziodoxaboroles, however, are indicative of significantly lower aromaticity compared to the classic aromatic systems. 相似文献
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Glen B. Robertson Uncharee Tooptakong John A. Lamberton Y.A. Geewananda P. Gunawardana I. Ralph C. Bick 《Tetrahedron letters》1984,25(25):2695-2696
X-ray crystallography shows that mearsine, a minor alkaloid of the north Queensland plant , has the novel isoquinuclidine structure 1, which permits charge transfer to take place between carbonyl and an azomethine group. 相似文献
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Reaction of sulfur dichloride with sym-EtO2CNHNHCO2Et 1 gives the title ring system which has been characterised by microanalyses, nmr, and X-Ray crystallography. The X-ray structure of S2[N(CO2Et)]4 2 reveals that the S2N4 ring adopts a chair conformation with all four ester groups in pseudo-axial positions. Bond lengths and angles are compared with 1 and S4(NR)2. 相似文献
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Yachnin BJ Sprules T McEvoy MB Lau PC Berghuis AM 《Journal of the American Chemical Society》2012,134(18):7788-7795
The Baeyer-Villiger monooxygenases (BVMOs) are a family of bacterial flavoproteins that catalyze the synthetically useful Baeyer-Villiger oxidation reaction. This involves the conversion of ketones into esters or cyclic ketones into lactones by introducing an oxygen atom adjacent to the carbonyl group. The BVMOs offer exquisite regio- and enantiospecificity while acting on a wide range of substrates. They use only NADPH and oxygen as cosubstrates, and produce only NADP(+) and water as byproducts, making them environmentally attractive for industrial purposes. Here, we report the first crystal structure of a BVMO, cyclohexanone monooxygenase (CHMO) from Rhodococcus sp. HI-31 in complex with its substrate, cyclohexanone, as well as NADP(+) and FAD, to 2.4 ? resolution. This structure shows a drastic rotation of the NADP(+) cofactor in comparison to previously reported NADP(+)-bound structures, as the nicotinamide moiety is no longer positioned above the flavin ring. Instead, the substrate, cyclohexanone, is found at this location, in an appropriate position for the formation of the Criegee intermediate. The rotation of NADP(+) permits the substrate to gain access to the reactive flavin peroxyanion intermediate while preventing it from diffusing out of the active site. The structure thus reveals the conformation of the enzyme during the key catalytic step. CHMO is proposed to undergo a series of conformational changes to gradually move the substrate from the solvent, via binding in a solvent excluded pocket that dictates the enzyme's chemospecificity, to a location above the flavin-peroxide adduct where catalysis occurs. 相似文献
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John A. Mosbo 《Magnetic resonance in chemistry : MRC》1978,11(6):281-286
The 220 MHz proton NMR spectra of three isomeric pairs of 2-R-2-oxo-4-methyl-1,3,2-dioxaphosphorinanes, where R = methoxy (1a, b), methyl (2a, b) and dimethylamino (3a, b) (a represents the trans and b the cis arrangement of R and the 4-methyl group) were analyzed by iterative computer techniques. Ten ring conformations, two chairs, two half-chairs and six boats were initially considered as being possible contributors to the overall solution conformations. Compounds 1a, 2a, 2b and 3b were all concluded to exist as single chair conformations with the 4-methyl group equatorially oriented (eqch). In addition to 68% of compound 3a being in that eqch conformation, however, significant concentrations of the chair form containing an axially oriented 4-methyl group (axch, 16%) and a boat conformation containing an equatorially oriented 4-methyl group with phosphorus and C-5 serving as the bow and stern (eq25, 16%) were also postulated. Similarly, it was suggested that 1b contained 60% eqch, 20% axch and 20% of the boat eq25. From the data for compounds 2a and b it was concluded that in the chair conformations of 2-oxo species the phosphorus substituent orientation has little effect upon the 3J(POCH) coupling constants. 相似文献
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p-Iodophenol and its O-MOM-protected ether can be converted into iodoamines 2. These give cross-conjugated ketones 3 on oxidation with hypervalent iodides in the presence of methanol, and the ketones undergo radical cyclization. Exposure of the products to acid or sequential treatment with a Grignard reagent and acid effects rearomatization to produce benzo-fused nitrogen heterocycles 4. 相似文献
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Willem A.L. van Otterlo E.Lindani NgidiCharles B. de Koning 《Tetrahedron letters》2003,44(34):6483-6486
The use of an aryl allyl ether and an arylallyl group as masked vinyl ether and 1-propenylphenyl groups for ring-closing metathesis (RCM) leading to the synthesis of benzo-fused heterocycles was demonstrated by using a ruthenium-mediated isomerization followed by a ruthenium-mediated RCM reaction. This resulted in the syntheses of a variety of products including two substituted benzo[1,4]dioxins, a naphtho[2,3-b][1,4]dioxin, a 2H-chromene and a benzo[b]furan. 相似文献