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We have studied the base-promoted heterocyclization of alkyl N-(cis(trans)-3,trans(cis)-4-dibromocyclohex-1-yl)carbamates and N-(cis(trans)-3,trans(cis)-4-dibromocyclohex-1-yl)-2,2,2-trifluoroacetamides, investigating the effect of the nitrogen protecting group and the relative configuration of the leaving group at C3 and C4 on the outcome of this reaction. We have observed that the sodium hydride-promoted heterocyclization of alkyl N-(cis-3,trans-4-dibromocyclohex-1-yl)carbamates (10, 12, 14, 16, 18) is a convenient method for the synthesis of 7-azabicyclo[2.2.1]heptane derivatives. For instance, the reaction of tert-butyl N-(cis-3,trans-4-dibromocyclohex-1-yl)carbamate (10) with sodium hydride in DMF at room temperature provides 2-bromo-7-[(tert-butoxy)carbonyl]-7-azabicyclo[2.2.1]heptane (2) (52% yield), whose t-BuOK-promoted hydrogen bromide elimination affords 7-[(tert-butoxy)carbonyl]-7-azabicyclo[2.2.1]hept-2-ene (31) in 78% yield, an intermediate in the total synthesis of epibatidine (1). However, the NaH/DMF-mediated heterocyclization of alkyl N-(trans-3,cis-4-dibromocyclohex-1-yl)carbamates (11, 13) is a more structure dependent reaction, where the nucleophilic attack of the oxygen atom of the protecting group controls the outcome of the reaction, giving rise to benzooxazolone and 2-oxa-4-azabicyclo[3.3.1]non-3-ene derivatives, respectively, from low to moderate yields, in complex reaction mixtures. Conversely, the NaH/DMF heterocyclizations of N-(cis-3,trans-4-dibromocyclohex-1-yl)-2,2,2-trifluoroacetamide (40) or N-(trans-3,cis-4-dibromocyclohex-1-yl)-2,2,2-trifluoroacetamide (42) are very clean reactions giving 7-azabicyclo[2.2.1]heptane or 2-oxa-4-azabicyclo[3.3.1]non-3-ene derivatives, respectively, in good yields. Finally, a mechanistic investigation, based on DFT calculations, has been carried out to rationalize the formation of the different adducts. 相似文献
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The reaction of the halobicyclobutane derivatives and with LDA in the presence of isoindoles afforded the azapropellanes and via the bicyclobutene intermediates and , respectively. 相似文献
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V. A. Vasin S. G. Kostryukov R. N. Zolotarev V. V. Razin 《Russian Journal of Organic Chemistry》2007,43(3):359-362
Successive treatment of 1-phenylsulfonyltricyclo[4.1.0.02,7]heptane with butyllithium and ethyl nitrate leads to the formation of 7-nitro-7′-phenylsulfonyl-1,1′-bi(tricyclo[4.1.0.02,7]heptane) through intermediate tricyclo[4.1.0.02,7]hept-1(7)-ene which is generated by 1,2-elimination of benzenesulfinic acid from the initial compound. Analogous treatment of 1-phenyltricyclo[4.1.0.02,7]heptane gives 1-nitro-7-phenyltricyclo[4.1.0.02,7]heptane. 相似文献
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The Stereoselective synthesis of cis and trans 2-methyl-1-phenyl-3-azabicyclo[3.1.0]hexanes and 1,2-diphen-yl-3-azabicyclo[3.1.0]hexanes from 2-oxo-1-phenyl-3-azabicyclo[3.1.0]hexane is described. The relative stereochemistry of the products was established by nuclear magnetic resonance and molecular modeling studies. 相似文献
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《Tetrahedron》1986,42(6):1687-1691
Molecular distortions in bridged [4.4]spirononanes and fenestranes are discussed in terms of symmetry deformation coordinates. This analysis reveals that the central, quaternary carbon atom in most of these compounds shows mainly a decrease of the two opposite ring bond angles, whereas the distortions in fenestranes are dominated by an increase of the two opposite bond angles. Dicyclopentadienone 8 serves as the starting material for the preparation of [5.5.5.5]fenestranes. In the key step of the synthesis, the Pd-catalyzed reductive transannular reaction of the enaminonitrile 13 and the ketolactone 17, (all-cis)[5.5.5.5]fenestrane 6 is formed instead of the (cis,cis,cis,trans)-isomer 7. 相似文献
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Verma SK Nguyen QH MacDougall JM Fleischer EB Moore HW 《The Journal of organic chemistry》2000,65(11):3379-3386
6-exo-Methylbicyclo[3.2.0]hepten-7-ones and their 2-alkylidene analogues are readily prepared from dialkyl squarates. These compounds undergo facial oxy-Cope ring expansions upon treatment with vinyllithium; the former leads to bicyclo[4.2. 1]non-1(4)-en-6-ones and the latter to the first examples of bicyclo[5.2.1]dec-1(10)-en-5-ones, compounds having exceptionally strained bridgehead double bonds. The transformations are controlled by the 6-exo-methyl group in the starting material along with the substituent at position-1 (bridgehead) which force attack of the lithium reagent from the concave face of the starting material, thus allowing the cyclopentenyl or alkylidene groups to participate in the sigmatropic event. 相似文献
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An acid-catalyzed Dieckmann-type reaction has been developed to access functionalized bicyclo[3.2.1]alkenediones. This methodology has been successfully extended to more substituted and larger ring homologues, providing a new and efficient route to the core of numerous attractive natural products and their analogues. 相似文献
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Wiberg KB 《The Journal of organic chemistry》2002,67(5):1613-1617
The acidities of 3- and 4-substituted bicyclooctane-1-carboxylic acids and 3-substituted bicyclo[1.1.1]pentane-1-carboxylic acids have been calculated at the MP2/6-311++G** theoretical level. There is good agreement between the calculated and observed gas-phase acidities. The acidities of the 4-substituted bicyclooctane acids were found to be linearly dependent on the C-X bond dipoles, as expected from a field effect. The substituents had a negligible effect on the electron density at C1. The difference in acidity between 4-chlorobicyclo[2.2.2]octane-1-carboxylic acid and the parent acid (6.2 kcal/mol) is reproduced by the Kirkwood-Westheimer treatment of substituent effects on acidity, but only if the bicyclooctane ring is given an effective dielectric constant of unity. The acidities of the 3-substituted bicyclooctane acids are linearly related to the corresponding 4-substituted acids with a slope of 0.9. The acidities of the 3-substituted bicyclo[1.1.1]pentane-1-carboxylic acids are linearly related to the C-X bond dipoles for this ring system (which are different than those for the bicyclooctanes), and they are also linearly related to the acidity of the 4-substituted bicyclo[2.2.2]octanecarboxylic acids with a slope of 1.34. The larger slope is due to the smaller bridgehead-bridgehead distance in the bicyclopentane ring than in bicyclo[2.2.2]octane. 相似文献
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Seyed Abolghasem Hashemi 《Tetrahedron letters》2012,53(38):5141-5143
A regioselective method for the synthesis of (E)-3-[2-(arylmethylene)-1-(arylsulfonyl)hydrazino]-2-propenoates is described. The reaction takes place between arylsulfonyl hydrazones and alkyl propiolates in the presence of triphenylphosphine as the catalyst. 相似文献
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N-Aroyl-3,5-dimethyl-and N-[N-arylsulfonylbenz(acet)imidoyl]-3,5-dimethyl-1,4-benzoquinone monoimines react with hydrazoic acid according to the 1,4-addition pattern. N-Acyl-2,3,5,6-tetrachloro-1,4-benzoquinone monoimines take up hydrazoic acid at the double C=N bond (1,2-addition). 相似文献
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Abstract In this communication we wish to report an interesting case of the isolation and characterization of the cis and trans isomers of 1-(p-bromobenzylidene)-2-indanone and their ketals. Prior to this work, Hoogstreen and Trenner2 had reported on the cis and trans isomers of 1-(p-chlorobenzylidene)-2-methyl-5-methoxyindenylacetic acid. The condensation of 2-(N-morpholinyl)-indene (1, prepared by the reaction of 2-indanone3 and morpholine) with P-bromobenzaldehyde was conducted by refluxing them in the presence of acetic acid for 4 hours. Acid hydrolysis of the reaction mixture followed by dry column chrcmatography over sillica gel using a fraction collector afforded two iscmeric monobenzylidenes, compounds 2(36.6%, mp 110–111°)and 3(1.3%, mp 115–116°) and a dibenylidene, compound 4 (8.7%, mp 205°). The relative rations of the mono- and dibenzylidenes seemed to depend on the reaction conditions. Higher yields of the monobenzylidenes 2 and 3 were obtained by conducting the reaction in the presence of UV light. The structures of these monobenzylidenes were established as cis and trans isomers of 1-(p-bromobenzylidenes)-2-indanone on the Basis of elemental analyses and ir and nmr spectroscopy. The ir spectra4 (CHCl3) of compounds 2 [1725 (c=0), 1620 (c=c)cm?1] and 3[1710 (c=o), 1570, 1600 (c=c) cm?1] were consistent with the structures. The molecular ion peaks as well as the fragmentation patterns in the mass spectra of both these compounds were consistent with the assigned structures. Before going into the omr discussion it should be pointed out that treatment of compound 2 with athylene glycol in the presence of p-toluene sulfonic acid produced two ketals, 5 (38.3% mp, 118–120°) and 6 (30.6% mp, 125–126°). As depicted; the ketals 5and 6 were also found (by omr) to be related to each other as cis and trans isomers. Furthermore, each of them could be hydrolyzed with acid to the corresponding monobenzylidenes 2 and 3 without any isomerization. However, UV irradiation of compounds 2 and 3 gave equilibrium mixtures containing both the isomers, indicating isomerization had occurred under photolytic conditions. 相似文献
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Philip Tarburton Lori J. Wolpa Robert K. Loerch Thomas L. Folsom Norman H. Cromwell 《Journal of heterocyclic chemistry》1977,14(7):1203-1207
The synthetic scope of the reaction of primary amines with α,β-dibromochalones to form aroylaziridines is explored and found to require at least one hydrogen on the α-carbon of the amine. Fourteen new epimeric l-alkyl-2-aryl(alkyl)-3-aroylaziridines are synthesized accordingly. Next, representative aroylaziridines are investigated by infra-red spectroscopy in solvents of ambient polarity to assess the relative populations of the gauche and cisoid conformers present in the (Z)-(cis) series. 相似文献
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Masafumi Ueda 《Tetrahedron letters》2008,49(41):5986-5989
A tricyclic substructure of the tetracyclic nitrogen core of the daphniglaucins was formed by an oxidative activation of the allyl side chain of a bicyclo[1.1.0]butylmethylamine, a spontaneous intramolecular formal Alder-ene reaction, and a selective cyclization of a triol intermediate. 相似文献