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1.
The hydrogenation of -6-methylenebicyclo[2,2,2]octan-2-ol catalysed by a range of rhodium and iridium complexes has been investigated. Unlike the corresponding -alcohol, reduction is highly stereoselective leading to 95 – 99.7% of -exo-6-methylbicyclo[2,2,2]octan-2-ol. Selectivity is much less pronounced for the corresponding methyl ether. Rhodium catalysts promote a competitive isomerisation of the double bond to -6-methyl-bicyclo[2,2,2]oct-5-en-2-ol, of which an authentic sample was reduced in high yield to pure - product. Reduction of both -hydroxy substrates by iridium complexes is rapid and highly selective.NMR studies employing europium shift reagents played a central part in defining the stereochemical interrelationships of 2,6-disubstituted bicyclo[2,2,2]octanes. 相似文献
2.
Cyclic enediol phosphoranes (2,2,2-trimethoxy-2,2-dihydro-l,3, 2-dioxaphospholenes), prepared from α-diketones, RCOCOR, and trimethyl phosphite (TMP), give strikingly different acylation products depending on the electronic properties of the groups, R, that occupy the 4,5-positions in the dioxaphospholene ring with pentacovalent phosphorus. Reaction of acetyl chloride or bromide with the hexafluorobiacetyl-TMP phosphorane gives exclusively the product of cyclic O-acylation, dimethyl(2-acetoxy--1,2, -trifluoromethylvinyl) phosphate. Acylation of the biacetyl-TMP phosphorane gives mixtures of the product of cyclic O-acylation (a cyclic enediol phosphate) and the product of C-acylation (an α-hydroxy-β-diketone phosphate), the proportions depending on the structure of the acyl halide and the solvent. The parent 1,3,2-dioxaphospholene, i.e., the glyoxal-TMP phosphorane where R = H, gives exclusively the product of cyclic O-acylation with both acyl halides in all solvents. 相似文献
3.
4.
Pyrolysis of 3-allylcyclopentanones affords -6-substituted bicyclo[2.2.1]heptan-2-ones. 相似文献
5.
The synthesis of a PGH2 analog 5-(2(Z), 6-(1E)-3-diazo-5-(7-hydroxy-2-heptenyl)-6-(3-hydroxy-1-octenyl)bicyclo[2.2.1]heptan-2-one 2 is described. 相似文献
6.
1,2,3,4,7,7-Hexafluorobicyclo[2,2,1]hepta-2,5-diene gave 1,2,3,4-tetrafluorebenzene in at least 73% yield when heated to 450°C in a sealed tube; the CF2 bridge appeared, in part, as octafluorocyclobutane. Nucleophilic attack by sodium methoxide- methanol on the diene occurred exclusively at the CFCF bond, causing the formation of 1,2,4,7,7-pentafluoro-3-methoxybicyclo- [2,2,1]hepta-2,5-diene and a 1,4,5,6,7,7-hexafluoro-5-methoxybicyclo [2,2,1]hept-2-ene thought, on the basis of 19F nmr data, to be the 6--F,5--MeO isomer. Radical attack on 1,2,3,- 4,7,7-hexafluorobicyclo[2,2,1]hepta-2,5-diene by bistrifluoromethyl nitroxide took place at both olefinic sites, with a . 10:1 preference for the CFCF linkage; all three geometrical isomers of 5,6-bis(bistrifluoromethylamino-oxy)-1,4,5,6,7,7- hexafluorobicyclo[2,2,1]hept-2-ene were formed. 相似文献
7.
4-Acetoxytricyclo[4.1.0.02,7]hept-4-en-3-one (), a valence isomer of 2-acetoxytropone, was synthesized. Upon heating in pyridine at 150°C, rearranged into 1-acetoxybicyclo[3.2.0]hepta-3,6-dien-2-one (); the mechanism of which was examined by means of deuterium labeling experiments. 相似文献
8.
Ratna Dasgupta Pranab R. Kanjilal Swapan K. Patra Manish Sarkar Usha Ranjan Ghatak 《Tetrahedron》1985,41(23):5619-5625
The efficacy of a new acid-catalyzed intramolecular C-alkylation has been demonstrated by the synthesis of 1-methyl-4--methoxyphenylbicyclo [2.2.2] octan-2-one () and 4--methoxyphenylbicyclo [2.2.2] octan-2-one () from easily accessible starting materials. The carbinol , derived from , undergoes facile rearrangement leading to 1--methoxyphenyl-4-methyl bicyclo [3.2.1] oct-3-ene (), which has been transformed to -1--methoxyphenyl-4-methylbicyclo [3.2.1] octan-3-one (). 相似文献
9.
The reaction of quadricyclane with difluorocarbene to give -6-(2,2-difluoro-vinyl)bicyclo[3.1.0]hex-2-ene (4) along with previously reported minor products is described and compared with earlier work. 相似文献
10.
Günter Kreiselmeier 《Tetrahedron》2006,62(25):6029-6035
The lithium aluminium hydride reduction of 2,2,4,4-tetrachloro-8-oxabicyclo[3.2.1]oct-6-en-3-one (8) was reinvestigated. In contrast to most halogeno-substituted oxabicyclic ketones, which give predominantly the corresponding endo alcohols, the expected (3endo)-2,2,4,4-tetrachloro-8-oxabicyclo[3.2.1]oct-6-en-3-ol (9n) is formed in a minute proportion. An X-ray structure analysis of the dominating product gave proof of the exo-alcohol, i.e., (3exo)-2,2,4,4-tetrachloro-8-oxabicyclo[3.2.1]oct-6-en-3-ol (9x). On the other hand, reduction of trichloroketone 11, 2,2,endo-4-trichloro-8-oxabicyclo[3.2.1]oct-6-en-3-one, and the methoxy-substituted chloroketones 13 and 14 provided the corresponding endo alcohols (12 and 15). 相似文献
11.
1,2-Dichloroethylene undergoes a stereospecific photoreaction with benzonitrile, the three tolunitriles, α,α,α-trifluorotoluene, fluorobenzene, and chlorobenzene to give substituted 6- 7- dichlorotricyclo[3,3,0,02,8]oct-3-enes which on treatment with base yield cyclised products or semibullvalenes: phenol yields dichlorobicyclo[3.2.1]oct-2-en-8-one with this ethylene photochemically. 相似文献
12.
The Mannich derivatives ( and ) of 9-acetyl-9,10-dihydroanthracene () with amines of different sizes were prepared for study of their biological effects. It was found that formation of the normal Mannich product in acetic acid was accompanied by formation of a secondary Mannich product containing a methylidene group ( and ). Reduction of compounds with NaBH4 gave aminoalcohols (), and amino-olefins () were prepared from these by elimination. The catalytic reduction of compounds on Pd/C, Raney Ni and Adams catalysts was studied under acidic and basic conditions. In acidic media on Pd/C, the 9,10-dihydro compounds () were formed; under basic conditions, on all three catalysts the hydrogenation led to deamination. However, for “steric hindrance” reasons the keto group was not reduced in any of the cases. In compounds , the literature data and the H-NMR spectra indicate that the orientation of the 9-substituent is pseudoaxial 相似文献
13.
Preparation of potential insect antijuvenile hormone agents 2,2-dimethyl-7-(2,2,2-trifluoroethoxy)-2H-chromene (), 6-methoxy-2,2-dimethyl-7-(2,2,2-trifluoroethoxy)-2-chromene () and 7-methoxy-2,2-dimethyl-6--(2,2,2-trifluoroethoxy)-2-chromene () and the corresponding 3,4-epoxides and is reported. 相似文献
14.
The stereochemistry and product distribution resulting from reaction of 4',5',6',7'- tetrahydrospirol[cyclopropane-1,2']-[4,7]methano[2]indene(5), endo-2-methyl(6a) and 2,2-dunethyl-4,7-dihydro-4,7-methano-2-indene (6b), as well as 4',5',6',7'-tetrahydrospiro[cyclopentane-1,2']-[4,7]methano-[2]indene (7) with singlet oxygen have been determined. Stereochemical assignments to the diepoxide products were readily deduced by 13C-NMR comparison with the spectra of the parent isomcrs of established structure (X-ray). To unravel the stereochemistry of the epoxy aldehydes, recourse was made to 2D NOE experiments The observed stereosclectivity and reaction profile of each substrate are analyzed and placed in proper mechanistic and energetic perspective. 相似文献
15.
An 1H n.m.r. study of (+)-muscarine 1 in deuterium oxide solution shows that the t conformation is highly favoured for the exocyclic C(5)-C(6) bond. Ring proton coupling constants can be accounted for on the basis of rapidly interconverting puckered forms largely favouring the C(4)- conformation. 相似文献
16.
Pyrolysis of the [2.2]paracyclophanyl diazomethane (1) at 270–300°C led to the product of carbon-hydrogen insertion (2) and -1,2-dehydro[3.2]paracyclophane (3). 相似文献
17.
Mass spectrometrical and 1H-NMR.-analyses of the exo-5-norbornen-2-yl acetate, formed by acetolysis of endo-5-norbornen-2-yl-2-exo-d brosylate, demonstrate that the deuterium initially on C(2) migrates partially (30%) onto C(1) (mechanism Ia or Ib). No deuterium could be detected on the other positions, which shows that C(1–7) migration is insignificant. 13C-NMR.-analysis of the deuteriated nortricyclyl acetate obtained as main product shows that the deuterium is equally and uniquely distributed between positions C(1) and C(6). This indicates that the nortricyclyl derivatives do not arise from nucleophilic attack on C(5) of asymmetrical norbornenyl intermediates, but from the reaction of a symmetrical nortricyclyl cation intermediate with solvent (mechanism Ib). Since the pioneering work of Roberts [1] and Winstein [2] on the solvolysis of exo- and endo-5-norbornen-2-yl derivatives 1-X and 2-X many papers have dealt with the cationic intermediate, the nature of which has still not been established satisfactorily [3]. We discuss briefly the main features of this homoallylic system and present experimental results that allow, for the first time, a clear distinction between five possible mechanisms Ia, Ib, II, III and IV of the degenerate rearrangement of the cationic intermediate formed in the acetolysis of the endo-5-norbornen-2-yl brosylate. 相似文献
18.
A.A.Leslie Gunatilaka Subramaniam Sotheeswaran H.T.Badra Sriyani Eric S. Waight 《Tetrahedron letters》1982,23(29):2987-2990
Hermonionic acid and its decarboxylated product have been isolated from . 13C NMR spectral and chemical evidence indicate that hermonionic acid is 2-0-[2-(3-methylbut-2-enyl)-3-methoxy- 4-hydroxy-5-(3,7-dimethylocta-2,6-dienyl]-4-methoxy-5-(3-methylbut-2-enyl-6-hydroxybenzoic acid. The previously assigned dienone structure for this acid is incorrect. 相似文献
19.
Reduction of 2-phenyl- and 2-methyl-exo-3,4-dichlorobicyclo[3.2.1]oct-2-enes with lithium aluminium hydride (LAH) or tributyltin hydride (TBTH) gave endo-2-phenyl-3-chlorobicyclo[3.2.1]oct-3-ene, 2-phenyl-3-chlorobicyclo[3.2.1]oct-2-ene and their methyl analogues. The action of both reagents on 2-phenyl-exo-3, 4-dibromobicyclo[3.2.1]oct-2-ene similarly resulted in reductive monodebromination to give normal and allylically rearranged products. Additionally, further reduction occurred to give endo-2-phenylbicyclo[3.2.1]oct-3-ene and 2-phenylbicyclo[3.2.1]-oct-2-ene. In all cases, LAH gave mainly the allylic rearrangement product whereas TBTH gave mostly unrearranged product. The reason for these differences could have been due either to the intervention of allylic radicals in the TBTH reduction or to differences in nucleophilicity. The results also show that LAH is equally efficaceous as TBTH in the reduction of these allylic halides and equally selective in the reduction of the vinyl bromides. The stereochemistry of the allylic rearrangement was shown to be synfacial in that hydride replaced halide on the same face of the molecule. 相似文献
20.
Reaction of the amines (CF3)2NX (X=Cl,Br) with norbornadiene either in solvent (CH2Cl2) at ?78 °C in the dark or in the vapour phase at 20 °C in daylight gives a mixture of 3-halogeno-5-(-bistrifluoromethylamino)nortricyclene (, -and , -isomers) and -5-(-bistrifluoromethylamino)- -7-halogenonorbornene in quantitative yield formed halonium ion addition to the diene. The reaction of the amine (CF3)2NBr in solvent Me2O or Et2O at ?78 °C in the dark gives the same products in low yield, together with 3-bromo-5-alkoxynortricyclene (, - and , -isomers) and the amine (CF3)2NR (R=Me, Et) in high yield. 相似文献