排序方式: 共有28条查询结果,搜索用时 265 毫秒
1.
Agnusdei M Bandini M Melloni A Umani-Ronchi A 《The Journal of organic chemistry》2003,68(18):7126-7129
A simple multistep synthetic strategy to 4-substituted 1,2,3,4-tetrahydro-beta-carboline and 1,3,4,9-tetrahydro-pyrano[3,4-b]indole derivatives starting from commercially available indole 2-carboxylic acid (5) is described. The final intramolecular Michael addition promoted by catalytic amount of InBr(3) (5-10 mol %) provided the expected polycyclic compounds in excellent yields (up to 97%) both in anhydrous organic and aqueous media. 相似文献
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Bandini M Fagioli M Garavelli M Melloni A Trigari V Umani-Ronchi A 《The Journal of organic chemistry》2004,69(22):7511-7518
A new catalytic system for the first example of enantioselective Friedel-Crafts-type (FC) addition of indoles to simple enones is described. The use of an equimolar amount of chiral [Al(salen)Cl] and 2,6-lutidine (10 mol %) was found to be effective in promoting the conjugate addition of indoles to (E)-arylcrotyl ketones, furnishing the corresponding beta-indolyl ketones in excellent yield and high enantioselectivity (ee up to 89%). The role of the base was investigated through spectroscopic as well as computational analyses, which suggested that in situ formation of a new chiral (base.[Al(salen)]) complex was operating under our reaction conditions. In particular, a stable cationic [Al(salen)] hexacoordinate trans complex with the additive base and the enone is suggested as being responsible for the stereocontrolled reaction. Finally, detailed monitoring of the reaction course was carried out showing that a conventional FC pathway induced by [Al(salen)Cl] acting as a Lewis acid is operating. 相似文献
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Melucci M Barbarella G Gazzano M Cavallini M Biscarini F Bongini A Piccinelli F Monari M Bandini M Umani-Ronchi A Biscarini P 《Chemistry (Weinheim an der Bergstrasse, Germany)》2006,12(28):7305-7312
A new class of chiral oligothiophenes is described. Mono-, bi-, ter-, and quarterthiophenes have been linked to enantiopure trans-1,2-cyclohexanediamine (DACH) via diamino or diimino moieties. The stereochemistry of DACH, the type of linker, and oligothiophene size determine the conformational flexibility of these molecules and consequently their molecular and supramolecular helicity in solution and in the solid state. The case of diaminobis(bithiophene), which inverts helicity and shows chiral amplification in the transition from solution to film, is described in detail. Based on the combined use of circular dichroism in solution and in the solid state, single-crystal/thin-film X-ray diffraction, and polarized optical microscopy, a working mechanism has been proposed to explain this unexpected behavior. 相似文献
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Gian Paolo Boldrini Achille Umani-Ronchi Mauro Panunzio 《Journal of organometallic chemistry》1979,171(1):85-88
The tetraethylammonium undecacarbonylhydridotriferrate [(C2H5)4N+ HFe3(CO)11?] (I): which can be easily prepared in a two-step sequence from iron pentacarbonyl, triethylamine and tetraethylammonium chloride, selectively reduces nitroarenes to amines and α, β-unsaturated carbonyl compounds to the corresponding saturated compounds both in good yield. I reacts with some organic halides to give dehalogenated products. 相似文献
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A new poly(ethylene glycol)-modified DAT2-Cu(OAc)2 complex smoothly catalyzes a base-free nitroaldol condensation in a highly enantioselective manner (ee up to 93%) also in reagent-grade solvent and in the presence of air. Effective recovery and recycling (up to five runs) of supported catalysts are documented. 相似文献
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Bandini M Cozzi PG Giacomini M Melchiorre P Selva S Umani-Ronchi A 《The Journal of organic chemistry》2002,67(11):3700-3704
Low sensitivity toward traces of moisture and high tolerance of different functional groups make indium tribromide suitable for carrying out multistep synthetic sequences. In particular, we have realized a 1,4-conjugated addition of indoles/thiols to alpha,beta-unsaturated ketones mediated by a catalytic amount (10 mol %) of InBr(3) obtaining the desired beta-substituted ketones in good yields. The Lewis acidity of indium salts was not affected by coordinating and acid nucleophiles; therefore, the subsequent catalytic 1,2-addition of Me(3)SiCN to carbonyl compounds can be performed in one pot. With the optimized atom-efficient protocol, several polyfunctionalized alpha-silyloxy cyanohydrins were synthesized in good to excellent yields (up to 97%) and a notable level of simple 1,3-diastereoselection (up to 84:16) was recorded in the case of 2-cyclohexen-1-one 2c. 相似文献
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Diego Savoia Emilio Tagliavini Claudio Trombini Achille Umani-Ronchi 《Journal of organometallic chemistry》1980,204(3):281-286
Highly dispersed potassium on alumina (K/Al2O3) acts as a metalating agent towards enolizable compounds and the intermediate organopotassium derivatives can be alkylated with primary alkyl bromides. The reaction conditions are dependent on the substrate. In particular, tetrahydrofuran is the solvent of choice for the metalation of nitriles and aldehydeN,N-dimethylhydrazones at ?60°C and of N-cyclohexyl ketimines at room temperature, whereas hexane must be used for ketones. 相似文献
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Gian Paolo Boldrini Diego Savoia Emilio Tagliavini Claudio Trombini Achille Umani-Ronchi 《Journal of organometallic chemistry》1985,280(3):307-312
The potassium—graphite route to active forms of metals has been extended to the preparation of titanium—graphite (Ti---Gr) and tin—graphite (Sn---Gr). The Ti---Gr is used to achieve the reductive coupling of ketones to give alkenes, and Sn---Gr is used in the preparation of diallyltin dibromide complexes which react with aldehydes to give homoallylic alcohols. 相似文献