The conformation of several -2,3-diaryloxy-1,4-dioxanes has been studied using 1H NMR techniques. -2,3-bis(4-nitrophenoxy)-1,4-dioxane and -2,3-bis(4-methoxyphenoxy)-1,4-dioxane have been found to be predominantly ( ≈98%) in diaxial conformation in CDCl3). On the other hand, -2,3-bis(2,6-dimethylphenoxy)-1,4-dioxane exists in the same conditions as a 66:33 mixture of diaxial and diequatorial conformers. An explanation based on the fulfilment of the exo-anomeric effect is provided. 相似文献
The Friedel-Crafts monoacylation of trans-η-[(1RS,2RS,4SR,5SR,6RS,7SR,8SR)-C,5,6,C-η:C,7,8,C-η-(5,6,7,8-tetramethylidene-2-bicyclo[2.2.2]octyl acetate)]-bis(tricarbonyliron) ((±)- 5 ) is highly stereoselective and yields trans-η-[(1RS,2RS,4RS,5SR,6RS,7RS,8SR)-C,6-η,oxo-σ:C,7,8,C-η-(6,7,8-trimethylidene-5-((Z)-2-oxopropylidene)-2-bicyclo[2.2.2]octyl acetate)]-bis(tricarbonyliron) ((±)- 8 ) which equilibrates with the trans-η-[(1RS,2RS,4RS,5SR,6RS,7RS,8SR)-C,5,6,C-η:C,7,8,C-η-(6,7,8-trimethylidene-5-((Z)-2-oxopropylidene)-2-bicyclo[2.2.2]octyl acetate)]-bis(tricarbonyliron) ((±)- 9 ) on heating. Optically pure (–)- 9 has been prepared from the corresponding optically pure alcohol (+)- 4 . The structure and absolute configuration of (–)- 9 was established by single-crystal X-ray diffraction. 相似文献
The crystal structure of a bis(triphenylphosphine)iminium salt of the 1:1 adduct of [FeH(CO)4]? and dimethyl acetylenecarboxylate has been determined from three-dimensional X-ray data collected by the counter method. Single crystals belong to the triclinic space space group P, with two units of [C36H30NP2]+[C10H7FeO8]? in a cell of dimensions: = 13.918(2), = 15.669(5), = 9.909(2) Å, = 91.22(3), = 94.83(2), and = 77.62(2)°. The structure was refined to a conventional of 0.068 for 5373 observed reflections. The resulting structure indicates that the complex anion is η3-[-2,3-bis(methoxycarbonyl)acryloyl]tricarbonylferrate, the coordination around the iron atom being described as a considerably distorted trigonal bipyramid. A comparison of the present structure with the structures of related complexes suggests that the η3-acryloyl portion is best represented as an intermediate of (η3-allyl) with the oxygen atom and (η2-olefin + η1-acyl). The short Fe-C(acyl) length of 1.897(5) Å implies an enhanced back-donation of electrons from the iron atom to the acyl group. 相似文献
Photochemical reaction between the enynes, (Z)-1-methoxybut-1-ene-3-yne, 1 or isopropenyl acetylene, 2 with CO in presence of Fe(CO)5 yields the 2,6- and 2,5-divinyl-substituted 1,4-benzoquinones: 2,6-bis{(Z)-2-methoxyvinyl}-1,4-benzoquinone (3, 42%), 2,5-bis{(Z)-2-methoxyvinyl}-1,4-benzoquinone (4, 31.5%), [{η2,η2:2,6-di(prop-1-en-2-yl)-1,4-benzoquinone}tricarbonyliron] (5, 45%), and {η2,η2:2,5-di(prop-1-en-2-yl)-1,4-benzoquinone}tricarbonyliron] (6, 65%). 相似文献
Ligand exchange reactions between phenanthrene or 9,10-dimethylphenanthrene with ferrocene effected in the presence of AlCl3-Al were carried out under a variety of conditions. With phenanthrene (I), hydrogenation at the C-9 and C-10 positions could take place during the reaction and the cationic products obtained were the η6-phenanthrene-η5-cyclopentadienyliron and η6-9,10-dihydro-phenanthrene-η5-cyclopentadienyliron moncations (II and III), and the η6-phenanthrene---η5-cyclopentadienyliron and η6-9,10-dihydrophenanthrene---η5-cyclopentadienyliron dications (IV and V). With 9,10-dimethylphenanthrene (VI), reactions carried out in refluxing cyclohexane gave the non-hydrogenated η6-9,10-dimethylphenanthrene-η5-cyclopentadienyliron monocation (VII) and η6-9,10-dimethylphenanthrene---η5-cyclopentadienyliron dication (VIII). When higher temperatures were used in an attempt to promote hydrogenation, decomposition predominated and no cationic product could be obtained. These finding are discussed and contrasted with previous results obtained from similar reactions using anthracene or 9,10-dimethylanthracene. 相似文献
Oxidation of the complexes -[M(CNR)2(dppe)2] (A) (M = Mo or W; R = Me, But or CH3C6H4-; dppe = Ph2PCH2CH2PPh2) with diiodine or silver (I) salts gives the paramagnetic cations -[M(CNR)2(dppe)2]+, (M = Mo, R = CH3C6H4-; M = W, R = But) and -[M(CNR)2(dppe)2]2+ (M = Mo, R = Me or CH3C6H4-; M = W, R = Me or But). Mixtures of products are generally produced when dichlorine or dibromine are the oxidising agents, however pure salts, the seven-coordinate complex cations [MX(CNC6H4CH3-)2(dppe)2]+ (B, X = Cl or Br) have been isolated. A simple molecular orbital scheme is proposed for complexes (A) and used to discuss their electronic spectra and their oxidation. 相似文献
-() and -1,3-Butadienylcyclobutane (), all--1-(1 ,3-butadieny1 )-2- vinylcyclobutane (), and all--1,2-bis(1,3-butadienyl)cyclobutane () have been prepared from readily available starting materials, and pyrolyzed to various cyclohexenes. 相似文献
Electron-deficient aromatics, such as 2,5-bis(trifluoromethylmercapto)thiophene () or (trifluoromethylmercapto)benzene (), react with F3CSCl in the presence of F3CSO3 as a catalyst to give mainly 3-chloro-2,5-bis(trifluoromethylmercapto)thiophen () and 1-chloro-4- or 2-(trifluoromethylmercapto)benzene (, respectively. This reaction competes with the one expected to result in 2,3,5-tris(trifluoromethylmercapto)thiophene () and 1,4- and 1,2-bis(trifluoromethylmercapto)benzene (,), respectively. Further reactions of deactivated aromatics with Cl3-nFnCSCl show that the chlorine substitution is in general catalysed by strong acids. Reaction mechanisms are proposed for both Substitutions. The Cl3-nFnCS group in aromatics exerts a -M-effect in the case of an attack of a positive ion, e.g. H⊕, the well-known +M-effect in the case of reactions with positively polarized molecules, e.g. CF3Sβ+Clβ-. 相似文献
Alkylation of lithiated -(benzyloxyacetyl)--2,5-bis(mehtoxyymethoxymethyl)- pyrrolidine proceeded with high stereoselectivity (≥96% de) and subsequent transformations of the alkylated products gave synthetically useful α-benzyloxy acids or α-hydroxy acids of high enantiomeric purity. 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 relative rates of formation of and [2+2]cycloadducts of benzyne to , - and , -1,5-cyclooctadiene, - and -cyclooctene are discussed and properties of the adducts (e.g., their unusual hydrogenation) are described. 相似文献
Optically pure (?)-trans-μ-[(1R,2R,3S,4S,5S,6R)-C,2,3,C-η:C,5,6,C-η-(2,3,5,6,7-pentamethylidenebicyclo[2.2.2]octane)]bis(tricarbonyliron) ((?)- 9 ), (?)-trans-μ-[(1R,2R,3S,4S,5S,6R,7S)-C,2,3,C-η:C,5,6,C-η-(7-methyl-2,3,5,6-tetramethylidenebicyclo[2.2.2]octane)]bis(tricarbonyliron) ((?)- 10 ), and (?)-trans-μ-[(1R,2R,3S,4S,5S,6R,7R)-C,2,3,C-η:C,5,6,C-η-(2,3,5,6-tetramethylidene(7D)bicyclo[2.2.2]octane)]bis(tricarbonyliron) ((?)- 16 ) have been prepared. Their CD spectra were solvent- and concentration-independent, but temperature-dependent, in accord with the existence of equilibria between rapidly interconverting diastereoisomeric species which can be interpreted as arising from distortions of the tricarbonyl(diene)iron units from the Cs symmetry. 相似文献
Bis(η4-cyclooctadiene-μ-methyleneiridium) reacts with acetylenes to yield various products. In the case of diphenylacetylene two compounds have been isolated from the reaction mixture and identified as a adduct containing a μ-η1, η3-1,2-diphenylallyl ligand (X-ray structure analysis), and as 1,2,4,5-tetraphenylbenzene. 相似文献
The reactions of (η5-C5H5)Co(CO)2 with both phenyl-1-naphthylacetylene and phenyl-2-naphthylacetylene have been shown to produce all four possible η5-cyclobutadiene-cobalt complexes and all six possible η4-cyclopentadienone-cobalt derivatives. The structures of the η4-cyclobutadiene-cobalt complexes have been assigned on the basis of proton NMR and mass spectral studies, and unequivocally established by means of an X-ray diffraction investigation for one of the isomers as (η5-cyclopentadienyl)[η4-1,3-di(1-naphthyl)-2,4-diphenylcyclobutadiene]cobalt. This compound is triclinic, a = 10.88(2), b = 15.710(6), c = 8.728(4) Å, α = 95.09(4)°, β = 101.94(2)°, γ = 86.93(3)°. The space group is P with Z = 2. The structure was solved by Patterson and Fourier methods and refined by full-matrix least squares methods (4128 reflections above 3σ) to a final R = 0.036. Bond distances and angles are normal but the cyclobutadiene ring is not quite planar. One of the atoms is 0.047 Å out of the plane of the other three apparently to relieve steric stress. The two phenyl rings are almost coplanar with the cyclobutadiene ring (torsion angles 3.9 and 20.4°) while the naphthyl rings are almost perpendicular to it (torsion angles 63.8, 64°). 相似文献
The Friedel-Crafts mono and double acylations of trans-μ-[(1RS,2RS,3SR,5RS,6SR,7SR)-C,2,3,C-η:C,6,7,C-η-(2,3,6,7-tetramethylidenebicyclo[3.2.1]octane)]bis(tricarbonyliron) ( 4 ) are highly stereoselective and yield trans-μ-{(1RS,2RS,3SR,5RS,6SR,7RS)-C,2,3,C-η :C,6,7,C-η-[(Z)-1-(3,6,7-trimethylidenebicyclo[3.2.1]-oct-2-ylidene)-2-propanone]}bis(tricarbonyliron) ( 5 ) and trans-μ-{(1RS,2RS,3SR,5RS,6SR,7SR)-C,2,3,C-η :C,6,7,C-η-[(Z,Z)-1,1′-(3,7-dimethylidenebicyclo [3.2.1] octane-2,6-diylidene)di(2-propanone)]}bis(tricarbonyliron) ( 6 ) whose structure has been established by single-crystal X-ray diffraction. 相似文献
1,4-Dibromo- (8) as well as 1,4,7-trichloro- (11a) and 1,4,7-tribromotriquinacene (11b) react with Fe2(CO)9 in THF to yield (dihydroacepentalene)hexacarbonyldiiron complexes 9 and 10, the first representatives with a 7,10-dihydroacepentalene ligand. By reaction with Fe2(CO)9, the readily accessible 4,7-bis (dialkylamino)tricyclo[5.2.1.04.10]deca-1(10),2,5,8-tetraenes 14, derivatives of the unknown 4,7-dihydroacepentalene, were transfomed into their tricarbonyliron complexes 15. Upon reduction with sodium in THF, the η4-(diene)tricarbonyliron 15 selectively gave the novel 1,10η2-(olefin)tricarbonylferrates(-2)17 as a result of a twofold electron transfer. The intermediate green radical anion 16, which is persistent in the absence of excess sodium, was characterized by its ESR signal. Complexes 17 are the first of their class with complete structural characterization by 1H- and 13C-NMR spectroscopy. 相似文献
2,2,2-Trifluorodiazoethane reacts with trifluoroacetonitrile in the dark at room temperature to give a 2-(2,2,2-trifluoroethyl)-4, 5-bis(trifluoromethyl)triazole, the 1,2,3-triazole structure being preferred to the 1,2,4-isomer on the basis of the 19F n.m.r. spectrum. The diazoethane reacts more slowly with trichloroacetonitrile, again forming the N-alkylated triazole even in the presence of an excess of the nitrile. No identifiable adduct resulted with acetonitrile. Hexafluoroisopropyl-ideneimine is first N-alkylated and then undergoes addition to form 1-(2,2,2-trifluoro-1-trifluoromethyl)ethyl-4,5-bis(trifluoromethyl)-?-1,2,3-triazoline, but N-methylhexafluoroisopropylideneimine failed to react. Trifluoroacetaldehyde and trichloroacetaldehyde give mixtures of the ketone (formed by insertion of the CF3CH group into the aldehyde CH bond) and the - and -oxirans, apparently a β-hydroxydiazoalkane. 相似文献
The 1-cyano-1-thiophenylcyclopentone derivative , obtained from (R,R)-(+)-tartaric acid, has been converted into a number of derivatives including the important -(3S,4S)-dibenzyloxycyclopentanone in 45% overall yield. 相似文献
Thermolysis of (η5-cyclopentadienyl)(triphenylphosphine)cobaltacyclopentadiene complexes has been found to give (η5-cyclopentadienyl)(η4-cyclobutadiene)-cobalt complexes in reasonable yields. Similar treatment of benzyl-substituted cyclopentadienyl derivatives gave diene complexes, (η5-C5H5CH2R1CR2CR3CHR4)Co, which were formed by addition of the ortho hydrogen of the benzyl group to the cobaltacyclopentadiene ring. 相似文献
The temperature-dependent 1H NMR spectra of acetylacetonatebis(ethylene)-rhodium, (acac)Rh(C2H4)2 (I), of some related complexes containing methoxy-substituted ethylenes have been measured in toluene-d8 solution. Both monosubstituted [(acac)Rh(C2H4)(olefin), olefin = tetramethoxyethylene (II), - and -dimethoxyethylene (III and IV)] and disubstituted [(acac)Rh(olefin)2, olefin = - and -dimethoxyethylene (V and VI), methyl vinyl ether (VII)] derivatives of I have been investigated with respect to hindered intramolecular movements of the ligands. The barriers of olefin rotation increase with an increasing number of methoxy substituents. When the olefin rotation is frozen out; the methoxy substituents of the olefins tend to be turned away from the acetylacetonate ligand unless steric interaction occurs between the two π-coordinated olefins. A hindered movement of the acetylacetonate ligand has been observed in II and V. For this movement which is independent of the olefin rotation, a degenerate rearrangement is proposed of the tetragonal-planar complexes via a tetrahedral transition state. 相似文献