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61.
62.
Reaction of β-naphthyl cinnamate with anhydrous aluminum chloride afforded 9-hydroxyphenalenone5 by a Fries rearrangement followed bya dearylative cyclisation. 9-Hydroxy-3-phenyl-2,3-dihydrophenaIen-l-one7 was identified as an intermediate. 相似文献
63.
Intramolecular cyclization of acyl(ethoxycarbonyl)keteneN-benzoylaminals in boiling Ph2O gives 5-acyl-4-amino-2-phenyl-1,3-oxazin-6-ones.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1322–1323, July, 1995.This study was financially supported by the Russian Foundation for Basic Research (Grant No. 94-03-08964). 相似文献
64.
Justicia J Rosales A Buñuel E Oller-López JL Valdivia M Haïdour A Oltra JE Barrero AF Cárdenas DJ Cuerva JM 《Chemistry (Weinheim an der Bergstrasse, Germany)》2004,10(7):1778-1788
The titanocene-catalyzed cascade cyclization of epoxypolyenes, which are easily prepared from commercially available polyprenoids, has proven to be a useful procedure for the synthesis of C(10), C(15), C(20), and C(30) terpenoids, including monocyclic, bicyclic, and tricyclic natural products. Both theoretical and experimental evidence suggests that this cyclization takes place in a nonconcerted fashion via discrete carbon-centered radicals. Nevertheless, the termination step of the process seems to be subjected to a kind of water-dependent control, which is unusual in free-radical chemistry. The catalytic cycle is based on the use of the novel combination Me(3)SiCl/2,4,6-collidine to regenerate the titanocene catalyst. In practice this procedure has several advantages: it takes place at room temperature under mild conditions compatible with different functional groups, uses inexpensive reagents, and its end step can easily be controlled to give exocyclic double bonds by simply excluding water from the medium. 相似文献
65.
Magali Szlosek-PinaudPhilippe Diaz Jean MartinezFrédéric Lamaty 《Tetrahedron letters》2003,44(48):8657-8659
A novel one-pot palladium-catalyzed cascade between 2-iodophenol, methyl bromomethylacrylate and an arylboronic acid provides an efficient access to heterocycles possessing the 3,3-disubstituted-2,3-dihydrobenzofuran skeleton via allylation/carbopalladation/Suzuki cross-coupling. 相似文献
66.
A novel approach has been found and the first total synthesis of (±)-Salvirecognine was accomplished by using it. In which intramolecular cyclization and Friedel-Crafts alkylation took place simultaneously to afford key intermediates for synthesis of aromatic tricyclic diterpenoids OMe PPA O O O OMe 1 2 Scheme 1 As shown in Scheme 1 intramolecular cyclization and Friedel-Crafts alkylation took place simultaneously when compound 1 was treated by PPA at 125 ℃. In which the i-pr… 相似文献
67.
Ring-closing metathesis (RCM) is the key step in a recently reported synthesis of salicylihalamide and related model compounds. Experimentally, the stereochemistry of the resulting cycloolefin (cis/trans) depends strongly on the substituents that are present in the diene substrate. To gain insight into the factors that govern the observed stereochemistry, density functional theory (DFT) calculations have been carried out for a simplified dichloro(2-propylidene)(imidazole-2-ylidene)ruthenium catalyst I, as well as for the real catalyst II with two mesityl substituents on the imidazole ring. Four model substrates are considered, which are closely related to the systems studied experimentally, and in each case, two pathways A and B are possible since the RCM reaction can be initiated by coordination of either of the two diene double bonds to the metal center. The first metathesis yields a carbene intermediate, which can then undergo a second metathesis by ring closure, metallacycle formation, and metallacycle cleavage to give the final cycloolefin complex. According to the DFT calculations, the stereochemistry is always determined in the second metathesis reaction, but the rate-determining step may be different for different catalysts, substrates, and pathways. The ancillary N-heterocyclic carbene ligand lies in the Ru-Cl-Cl plane in the simplified catalyst I, but is perpendicular to it in the real catalyst II, and this affects the relative energies of the relevant intermediates and transition states. Likewise, the introduction of methyl substituents in the diene substrates influences these relative energies appreciably. Good agreement with the experimentally observed stereochemistry is only found when using the real catalyst II and the largest model substrates in the DFT calculations. 相似文献
68.
采用NdCl3·3i-PrOH-AlEt3稀土催化剂进行丁二烯的顺式聚合,在聚合过程中引入烯丙基氯,进行分子内环化反应以及单体的环聚反应.考察了稀土催化剂用量、n(烯丙基氯)/n(AlEt3)、环化时间、反应温度、单体浓度等对环化反应的影响,并对产物进行了红外光谱、核磁共振光谱的表征 相似文献
69.
Steven R. Woodcock 《Tetrahedron letters》2005,46(42):7213-7215
Ether tethers allow Heck cyclizations to proceed in high yields. Ester tethers lead to low yields. Styrene trapping experiments indicate that ester reactions form viable organopalladium intermediates that cannot cyclize efficiently. 相似文献
70.
The regioselectivity of the reactions of perimidine with cinnamic acids in polyphosphoric acid (PPA) depends on the P2O5 content. Procedures were developed for the synthesis of 4(9)- and 6(7)-cinnamoylperimidines. Cyclization of the latter under the action of an excess of AlBr3 was accompanied by dearylation to form 6-hydroxy-1,3-diazapyrene. 相似文献