The radical cation of bicyclo[2-2.1]hepta-2,5-diene (8,9,10-trinorborna-2,5-diene; 1 ) in CF2ClCFCl2, and CF3CCl3 matrices and that of bicyclo[2.2.2]octa-2,5-diene (2,3-dihydrobarrelene; 2 ) in CFCl3 and CF3CCl3 matrices have been studied by ESR and ENDOR spectroscopy. For ${\bf 1}^{+ \atop \dot{}}$, the coupling constants of the olefinic, methano-bridge, and bridgehead protons are ?0.780 ±0.005, +0.304±0.002, and ?0.049±0.002 mT, respectively. The hyperfine tensor for the methano-bridge protons is axial, Ax = +0.263 ± 0.002 and Ay = +0.386 ± 0.002 mT, while that for the olefinic protons is orthorhombic, Ax = ?0.594 ± 0.005, Ay= ?0.913 ± 0.005, and Az = ?0.834 ± 0.005 mT (x parallel to C? H- z parallel to 2pπ axis). For ${\bf 2}^{+ \atop \dot{}}$, the coupling constants of the olefinic, ethano-bridge, and bridgehead protons are ?0.68 ± 0.01, +0.162 ± 0.005, and ?0.108 ± 0.005 mT, respectively. The hyperfine data for ${\bf 1}^{+ \atop \dot{}}$ and ${\bf 2}^{+ \atop \dot{}}$ fully support the presentation of their singly occupied orbitals as antisymmetric combinations, b2(π), of the two bonding ethene π-MO's. 相似文献
This article is a continuation of our investigation of enthalpies of formation and strain-compensated enthalpies of hydrogenation of medium-sized hydrocarbons. We have carried out calculations of Hf by MM2, MM3, and by the MNDO, AM1, and PM3 semi-empirical molecular orbital methods. Results are given for the bicyclo[2.2]octa-2,5,7-triene series ([2.2.2]barrelenes) Two of these compounds are potentially homoantiaromatic. Comparisons with ab initio calculations are made. A novel method of estimating strain relaxation during the stepwise hydrogenation of [2.2.2]barrelene is given. 相似文献
Dibenzo[b,e]-7,7,8,8-tetraalkyl-7,8-disilabicyclo[2.2.2]octa-2,5-dienes (1: R = tBuCH2; 2: R = iPr) were prepared by the reaction of ClR2SiSiR2Cl with lithium anthracenide in 1,2-dimethoxyethane (DME) at room temperature. The structure of 1 was determined by X-ray crystallography. Crystal data for 1: monoclinic, rC2/c, A = 12.941(2), B = 14.601(1), C = 35.109(6) Å, β = 94.957(7)°, V = 6609(2) Å3, Z= 8, R = 0.048, Rw = 0.053 for 4037 reflections. Compounds 1 and 2 show the bathochromic shift of 1La and 1Lb bands in UV spectra and exhibit considerably low oxidation potentials due to effective σ-π conjugation. Compounds 1 and 2 form charge-transfer complexes with tetracyanoethylene (TCNE). In the case of 1, the charge-transfer complex (1: TCNE = 2: 1) could be isolated as crystals and the structure was determined by X-ray crystallography. Crystal data for the 1-TCNE complex: monoclinic, C2/c, A= 10.267(2), b = 36.077(4), C = 20.022(4) Å, β = 100.680(8)°, V = 7288(2) Å3, Z = 4, R = 0.045, Rw = 0.077 for 4120 reflections. The action of transition metal chlorides on 2 resulted in [4+2] cycloreversion to form CliPr2SiSiiPr2Cl and anthracene. 相似文献
The regioselectivity and stereochemistry of the reaction of mercuric salts with dimethyl bicyclo[2.2.2.]octa-2,5-diene-5,6-dicarboxylate were studied in different solvents. The factors determining the reaction regioselectivity were considered.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1642–1645, September, 1993. 相似文献
The 7,8-bis(benzyloxy)bicyclo[2.2.2]octa-2,5-diene derivatives have been synthesized via Diels-Alder reaction of optically active 5,6-bis(benzyloxy)cyclohexa-1,3-diene and dienophiles. The corresponding tricarbonyliron complexes have also been synthesized in enantiomerically pure form. 相似文献
[reaction: see text] C2-symmetric bicyclo[2.2.2]octa-2,5-dienes containing benzyl, phenyl, and substituted phenyl groups at 2 and 5 positions were prepared enantiomerically pure by way of bicyclo[2.2.2]octane-2,5-dione as a key intermediate. These chiral diene ligands were successfully applied to rhodium-catalyzed asymmetric 1,4-addition of arylboronic acids to alpha,beta-unsaturated ketones. High enantioselectivity (up to 99% ee) as well as high catalytic activity was observed in the addition to both cyclic and linear substrates. 相似文献
Enzymatic desymmetrization of the title compound 1 is reported using various commercially available lipases in hydrolysis and alcoholysis reactions or ester synthesis. In this area, lipase Amano AK (Pseudomonas sp.) proved to be the best lipase whatever the experimental conditions used. The monoacetate product 2 is indifferently obtained with more than 95% enantiomeric excess (ee) as the levorotatory enantiomer 2a or the dextrorotatory one 2b. 相似文献
The transition-metal-catalyzed [4 + 2 + 2] cycloadditions of norbornadienes, bicyclo[2.2.2]octa-2,5-diene, and benzobarrelene with 1,3-butadienes proceed in excellent yields using cobalt-based catalytic systems. Two key distinctions between these [4 + 2 + 2] cycloadditions and the corresponding transition-metal-catalyzed [2 + 2 +2] reactions of norbornadiene are the requirement of a bimetal catalytic system with a bisphosphine ligand for the former and exclusive regioselectivity in the [4 + 2 + 2] reaction of 2-substituted norbornadienes to produce 1-substituted adducts. These distinctions may indicate two distinct mechanisms for the [4 + 2 + 2] and [2 + 2 + 2] reactions. 相似文献
Treatment of 3-bromo-6,7-benzobicyclo [3.2.1] octa-2,3-diene (9) with potassium tert.-butoxide produces the strained bicyclic allene (10) which is trapped by 1,3-diphenylbenzo[c]furan (DBI) to give five isomeric cycloadducts. In the absence of DBI, allene (10) gave rise to enol ether (18) by addition of tert.-butanol. 相似文献
Norbornadienes that feature the properties of norbornadiene and of the ene-diyne in the same molecule have been prepared via a simple and high-yielding route starting fromdichlorobicyclo[2.2.1]hepta-2,5-diene (1). 相似文献
Treatment of 1,2-di-t-butyl-1,2-dicyclohexyl-1,2-dichlorodisilane (5b) with excess lithium yields the long-lived radical anion t-Bu(Cy)SiSi(Cy)t-Bu , which has been characterized by its ESR spectra. Reaction of 5 as well as 1,1,2,2-tetracyclohexyl-1,2-dihalodisilanes (6) with lithium in the presence of anthracene gives 7,8-tetraorganyl-2,3 : 5,6-dibenzo-7,8-disilabicyclo[2.2.2]octa-2,5-dienes which can be cleaved photochemically forming the corresponding cyclotetrasilanes. In the presence of phenylacetylene 5 and 6 react with lithium to give the 1,2-bis(phenylethinyl)-substituted disilanes and 3,4,5,6-tetra-t-butyl-3,4,5,6-tetracyclohexyl-2-phenyl-3,4,5,6-tetrasilacyclohexen-1, respectively. The latter compound is also obtained by phenyl-acetylene insertion into 1,2,3,4-tetra-t-butyl-1,2,3,4-tetracyclohexylcyclotetrasilane. 相似文献