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71.
Donatella Banti 《Tetrahedron》2004,60(37):8043-8052
Norbornene derivatives bearing endo-substituents in the 5- and 6-positions were studied as substrates for ene-yne metathesis cascades. Substrates which contained an internal alkyne and a terminal alkene or alkyne in each sidechain were found to undergo a metathesis cascade leading to pentacyclic bis-dienes and bis-trienes. Attempts to extend the chemistry further to sidechains containing two internal alkynes or two internal alkynes and a terminal alkene were not successful with the first generation Grubbs' catalyst. However, the substrate containing two internal alkynes did react with the second generation Grubbs' catalyst to give a tetra-diene containing product. 相似文献
72.
Vincenzo G Albano Fabio Marchetti Stefano Zacchini 《Journal of organometallic chemistry》2004,689(3):528-538
Terminal alkynes (HCCR′) (R′=COOMe, CH2OH) insert into the metal-carbyne bond of the diiron complexes [Fe2{μ-CN(Me)(R)}(μ-CO)(CO)(NCMe)(Cp)2][SO3CF3] (R=Xyl, 1a; CH2Ph, 1b; Me, 1c; Xyl=2,6-Me2C6H3), affording the corresponding μ-vinyliminium complexes [Fe2{μ-σ:η3-C(R′)CHCN(Me)(R)}(μ-CO)(CO)(Cp)2][SO3CF3] (R=Xyl, R′=COOMe, 2; R=CH2Ph, R′=COOMe, 3; R=Me, R′=COOMe, 4; R=Xyl, R′=CH2OH, 5; R=Me, R′=CH2OH, 6). The insertion is regiospecific and C-C bond formation selectively occurs between the carbyne carbon and the CH moiety of the alkyne. Disubstituted alkynes (R′CCR′) also insert into the metal-carbyne bond leading to the formation of [Fe2{μ-σ:η3-C(R′)C(R′)CN(Me)(R)}(μ-CO)(CO)(Cp)2][SO3CF3] (R′=Me, R=Xyl, 8; R′=Et, R=Xyl, 9; R′=COOMe, R=Xyl, 10; R′=COOMe, R=CH2Ph, 11; R′=COOMe, R=Me, 12). Complexes 2, 3, 5, 8, 9 and 11, in which the iminium nitrogen is unsymmetrically substituted, give rise to E and/or Z isomers. When iminium substituents are Me and Xyl, the NMR and structural investigations (X-ray structure analysis of 2 and 8) indicate that complexes obtained from terminal alkynes preferentially adopt the E configuration, whereas those derived from internal alkynes are exclusively Z. In complexes 8 and 9, trans and cis isomers have been observed, by NMR spectroscopy, and the structures of trans-8 and cis-8 have been determined by X-ray diffraction studies. Trans to cis isomerization occurs upon heating in THF at reflux temperature. In contrast to the case of HCCR′, the insertion of 2-hexyne is not regiospecific: both [Fe2{μ-σ:η3-C(CH2CH2CH3)C(Me)CN(Me)(R)}(μ-CO)(CO)(Cp)2][SO3CF3] (R=Xyl, 13; R=Me, 15) and [Fe2{μ-σ:η3-C(Me)C(CH2CH2CH3)CN(Me)(R)}(μ-CO)(CO)(Cp)2][SO3CF3] (R=Xyl, 14, R=Me, 16) are obtained and these compounds are present in solution as a mixture of cis and trans isomers, with predominance of the former. 相似文献
73.
A novel end-capping method of pseudorotaxanes via the hydrosilylation of the alkyne of the axle terminal was developed. RuHCl(CO)(PPh3)3 and RhCl(CO)(PPh3)3 complexes catalyzed the hydrosilylation reactions of the alkyne moiety of several pseudorotaxanes at ambient temperature to give the corresponding [2]- and higher order rotaxanes in high yields with excellent regio- and stereoselectivity. 相似文献
74.
[1-Phenyl-2-[(E)-3-phenylprop-2-en-1-oyl-κO]ethenyl-κC1]tetracarbonylmanganese (1a) reacts with PhCCH in CCl4 at room temperature to form [2,4-diphenyl-6-(2-phenylethenyl)pyranyl-η5]tricarbonylmanganese (2a), whose X-ray crystal structure is reported to complement that of its isomer [6-oxo-2,4,7-triphenylcyclohepta-1,4-dienyl-1,2,3,4,5-η]tricarbonylmanganese (3a), previously obtained from the reaction under reflux; but for 1a and PhCCPh the pyranyl complex cannot be isolated before rearrangement to the 3a analogue occurs. More forcing reaction conditions for 1a with Me3SiCCH and for [1-(2-trifluoromethylphenyl)-2-[(E)-3-(2-trifluoromethylphenyl)prop-2-en-1-oyl-κO]ethenyl-κC1]tetracarbonylmanganese (1b) with Me3SiCCH and PhCCH give new analogues of 3a where previously only 2a analogues had been isolated.The reaction in CCl4 under reflux of PhCCH and the β-deuterio analogue of 1a, [1-phenyl-2-[(E)-3-phenylprop-2-en-1-oyl-3d-κO]ethenyl-κC1]tetracarbonylmanganese, gave deuteriated 3a with exo-D at the α-carbon, C7. This is inconsistent with the Mn-mediated Ph migration mechanism originally proposed to accommodate the endo position of Ph in 3a, and instead it implicates a cyclopropyl carbonyl-addition intermediate or a cyclopropyl acyl-substitution transition state in the key rearrangement step for 2a → 3a. 相似文献
75.
76.
Nitin T. Patil 《Tetrahedron letters》2004,45(46):8497-8499
An efficient method for the allylation of C, N, and O-nucleophiles with alkynes under solvent-free conditions and by microwave activation is established. The process can be termed as a real eco-chemical process since no waste elements are produced in the reaction, moreover it is solvent free. This technique can also be used for the allylation of dimethyl methylmalonate, which proves inert under the previously reported reaction conditions (refluxing in 1,4-dioxane). 相似文献
77.
A three-component coupling of aldehyde, alkyne, and amine was developed by using gold, copper, or silver as catalysts in ionic liquid. 相似文献
78.
A facile synthesis of an enantiomerically pure 3,3′-bismorpholinylmethyl H8-BINOL ligand has been developed. This compound in combination with Et2Zn and Ti(OiPr)4 is found to catalyze the highly enantioselective reaction of phenylacetylene with aromatic aldehydes. The enantioselectivity of this catalytic process for the reactions of ortho-substituted benzaldehydes is significantly higher than that based on H8-BINOL. 相似文献
79.
Juan Francisco González 《Tetrahedron》2004,60(30):6319-6326
The behavior of aldehydes and acetals as N-alkylating agents of 1-acetyl-3-arylmethylpiperazine-2,5-diones and the subsequent cyclization of the N-alkylated products was studied. Use of paraformaldehyde in different reaction conditions gave 6-unsubstituted 3,6,11,11a-tetrahydro-2H-pyrazino[1,2-b]isoquinoline-1,4-diones and, in some cases, benzo[f]pyrazino[1,2-c]1,3-oxazepine-1,4-diones. Succesful reactions with benzaldehyde required a first activation of the lactam function and a catalyzed N-alkylation with the aldehyde dimethyl acetal. The isolated O,N-amidoacetals thus obtained were submitted to a diastereoselective Pictet Spengler-type reaction that worked with arenes at several degrees of ring activation and with thiophene to give 6-phenylpyrazinoisoquinolinediones and the corresponding thieno analog. 相似文献
80.
The reaction of hexachlorotropone with trimethylsilylethynyl-lithium leads to contraction of the seven-membered ring via a semibenzilic acid rearrangement to yield pentachlorophenyl trimethylsilylethynyl ketone, 4. Treatment of 4 with dicobalt octacarbonyl yields the corresponding alkyne-dicobalt hexacarbonyl, 6, which has been characterized by X-ray crystallography. 相似文献