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1.
Sagae H Noguchi K Hirano M Tanaka K 《Chemical communications (Cambridge, England)》2008,(32):3804-3806
A cationic rhodium(i)/(R)-H(8)-BINAP or (R)-Segphos complex catalyzes an intramolecular [2 + 2 + 2] cycloaddition of unsymmetrical dienynes, leading to fused tri- and tetracyclic cyclohexenes bearing two tertiary or quaternary carbon centers in high yields with high enantio- and diastereoselectivity. 相似文献
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[reaction: see text] [Ir(cod)Cl]2/DPPE was found to be a new catalyst for the cycloaddition of alpha,omega-diynes with monoynes to give polysubstituted benzene derivatives in high yields. Internal monoynes as well as terminal monoynes could be used. The reaction tolerates a broad range of functional groups such as alcohol, amine, alkene, ether, halogen, and nitrile. The reaction of 1,6-octadiyne derivatives with 1-alkynes gives ortho products and meta products. The regioselectivity could be controlled by the choice of ligand. The reaction with DPPE was meta selective, with meta selectivity of up to 82%. The reaction with DPPF was ortho selective, with ortho selectivity of up to 88%. We propose a mechanism to account for this regioselective cycloaddition. [Ir(cod)Cl](2)/DPPE also catalyzed the cycloaddition of alpha,omega-diynes with 2,5-dihydrofuran to give bicyclic cyclohexadiene derivatives. The reaction with 2,3-dihydrofuran and n-butyl vinyl ether gave benzene derivatives instead of cyclohexadiene derivatives. We also propose a mechanism to account for this novel aromatization that includes cleavage of the C-O bond. 相似文献
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Axially chiral hydroxy carboxylic acid derivatives were successfully synthesized with high yields and ee values by the cationic rhodium(I)/axially chiral biaryl bisphosphine complex-catalyzed enantioselective [2 + 2 + 2] cycloaddition. Axially chiral hydroxy and dihydroxy carboxylic acid derivatives, bearing the aryl group at the ortho-position of the alkoxycarbonyl group, were also synthesized with high regio- and enantioselectivity. 相似文献
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The concise synthesis of axially chiral biaryl diphosphine ligands by the rhodium-catalyzed intramolecular [2 + 2 + 2] cycloaddition of hexayne diphosphine oxides has been achieved. These new chiral diphosphine ligands could be employed as a ligand for the rhodium-catalyzed asymmetric catalyses. 相似文献
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We have developed a rhodium-catalyzed enantioselective intermolecular [2+2+2] cycloaddition of 1,6-diynes with trimethylsilylynamides for the synthesis of axially chiral anilides. The axial chirality is constructed at the formation of benzene rings with high enantioselectivity (up to 98% ee). It should be noted that the present reaction employs the readily prepared trimethylsilylynamides starting from commercially available bis(trimethysilyl)acetylene and the trimethylsilyl group of the product anilides is expected to be utilized for further functionalization. 相似文献
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[reaction: see text] Highly selective cross [2 + 2 + 2] cycloaddition of two different monoynes is achieved by using a catalytic amount of [Ir(cod)Cl](2) and ligand. The ligand had a considerable effect on the reaction. When 1,2-bis(diphenylphosphino)ethane was used, two molecules of dimethyl acetylenedicarboxylate (DMAD) reacted with one molecule of a monoyne to give the 2:1 coupling product. When 1,2-bis(dipentafluorophenylphosphino)ethane was used instead of dppe, one molecule of DMAD reacted with two molecules of a monoyne to give the 1:2 coupling product. 相似文献
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Facile synthesis of naphthoquinone spiroketals by diastereoselective oxidative [3 + 2] cycloaddition
A highly selective oxidative [3 + 2] cycloaddition of chiral enol ethers and hydroxynaphthoquinone is described. This convergent strategy is amenable to an enantioselective synthesis of beta-rubromycin and related naphthoquinone spiroketals. Several compounds were found to inhibit DNA-polymerase and telomerase in a manner resembling alpha-rubromycin and beta-rubromycin. 相似文献
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Barluenga J Fernández-Rodríguez MA Aguilar E Fernández-Marí F Salinas A Olano B 《Chemistry (Weinheim an der Bergstrasse, Germany)》2001,7(16):3533-3544
A new procedure for the synthesis of 1,3,4-trisubstituted and 1,4-disubstituted pyrrolidin-2-one derivatives in an enantioselective fashion is reported. The 1,3-dipolar cycloaddition of (+/-)-menthol and (-)-8-phenylmenthol derived Fischer alkoxy alkenyl carbene complexes with in situ generated functionalized azomethine ylides gives the corresponding cycloadducts as chelated tetracarbonyl Fischer carbene complexes. Only one regioisomer is detected in all cases, and the diastereoselectivity of the reaction is very high when (-)-8-phenylmenthol derived carbenes are employed. Oxidation and further transformation of the cycloadducts provide an easy access to pyrrolidin-2-ones. The anti-inflammatory and antidepressant drug (+)-Rolipram is readily prepared in four steps in a 20% overall yield by taking advantage of this newly developed methodology. 相似文献
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A total synthesis of daunosamine (3) and acosamine (4) has been accomplished via a diastereoselective intramolecular nitrone-olefin cyclization. In the key step the chiral nitrone 12a cyclized to give two isoxazolidines 13a and 14a in an 82:18 ratio. Further elaboration of 13a led to daunosamine and acosamine. The effects of olefin substitution on the diastereoselectivity of the cycloaddition was also examined. 相似文献
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《Tetrahedron: Asymmetry》2006,17(4):614-619
An iridium-chiral diphosphine complex was used to catalyze an enantioselective [2+2+2] cycloaddition of oxygen- and nitrogen-bridged triynes with ortho-substituted aryl groups on their termini. ortho-Diarylbenzenes with atropisomeric chiralities were obtained in high yield and enantiomeric excess. 相似文献
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The enantioselective intramolecular [2 + 2 + 2] cycloaddition of various enediynes, where two acetylenic moieties are connected by a trans-olefinic moiety, gave chiral tricyclic cyclohexa-1,3-dienes using Rh-H8-BINAP catalyst. In the case of carbon-atom-tethered enediynes, enantioselectivity was generally good-to-high regardless of the substituents on their alkyne termini. In contrast, with heteroatom-tethered enediynes, appropriate substituents were required to induce the oxidative coupling of alkyne and alkene moieties before that of two alkyne moieties, which would be important for highly enantioselective intramolecular cycloaddition. 相似文献
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Takanori Shibata Shiho Yoshida Yoshikazu Arai Maiko Otsuka Kohei Endo 《Tetrahedron》2008,64(5):821-830
A chiral iridium complex catalyzed a consecutive and enantioselective [2+2+2] cycloaddition of polyynes to give axially chiral compounds. Intermolecular reaction of tetraynes, possessing aryl groups on their termini, with protected but-2-yne-1,4-diols gave C2-symmetrical quateraryl compounds. Intramolecular reaction of hexaynes, possessing aryl or alkyl groups on their termini gave C2-symmetrical biaryl compounds. The catalytic synthesis of a pentacene derivative with axial chiralities is also discussed. 相似文献
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A cationic rhodium(I)/Segphos complex catalyzes a [2 + 2 + 2] cycloaddition of internal 1,6-diynes with a phosphonate- or ester-substituted 1,3-butadiyne leading to C(2)-symmetric axially chiral biaryl diphosphonates or dicarboxylates, respectively, in high yields with outstanding ee's. The use of a phosphonate- or ester-substituted 1,3-butadiyne as a cycloaddition partner and Segphos as a ligand is crucial for the success of this transformation. 相似文献
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Hiroyoshi KitanoShinya Fujita Yutaka TakeharaMasakazu Hattori Toshio MoritaKazutsugu Matsumoto Minoru Hatanaka 《Tetrahedron》2003,59(15):2673-2677
4-Alkenylfulvenes were prepared by the annulation of 1,4-ynediones and allylidenetriphenylphosphorane and subjected to a thermal reaction. Highly regio- and stereoselective [4+2] cycloaddition is accomplished with 4-((R)-3-benzyloxypent-4-en-1-yl)fulvene and the resulting adduct is transformed into bicyclo[3.3.0]octene derivative. 相似文献
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Nickel(0) catalyzed [4+2] cycloaddition of electron-deficient dienes to alkynes and subsequent aromatization gave highly substituted arenes. This formal inverse electron-demand Diels-Alder cycloaddition is attributed to the formation of a seven-membered nickelacycle from a diene and an alkyne. 相似文献
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A catalytic cascade synthesis of isoxazoline-N-oxide was developed through proline-catalyzed nitroalkene activation. A large substrate scope was obtained with good to excellent yields. Mechanistic studies revealed intramolecular cyclization as the rate-determining step, giving only trans isomers in all cases. 相似文献