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1.
In conjunction with iodoxybenzene as reoxidant perfluorooctylseleninic acid catalyzes the allylic oxidation of alkenes to enones in trifluoromethylbenzene at reflux in moderate to good yield. After a reductive workup with sodium metabisulfite, the catalyst is recovered by fluorous extraction in the form of bis(perfluorooctyl) diselenide, which, itself, serves as a convenient catalyst precursor. [reaction: see text] 相似文献
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A substoichiometric amount of titanium-TADDOLate complex was effective at catalyzing the cyclopropanation reaction of allylic alcohols in the presence 1 equiv of bis(iodomethyl)zinc. After initial optimization of the catalyst structure, excellent yields and enantiomeric ratios were obtained for 3-aryl- or 3-heteroaryl-substituted allylic alcohols (up to 97:3). Alkyl-substituted allylic alcohols gave modest yields and enantiomeric ratios (up to 87:13) but these compare favorably with those observed with other substoichiometric chiral ligands. The full synthetic scope of the reaction is presented in this paper. 相似文献
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Lafrance M Roggen M Carreira EM 《Angewandte Chemie (International ed. in English)》2012,51(14):3470-3473
The direct route: Iridium-catalyzed direct conversion of branched allylic alcohols into enantioenriched branched primary allylic amines is highly regio- and enantioselective (see scheme; coe=cyclooctene). 相似文献
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The preparation of various (R)-Sulfur-MOP ligands with aryl and alkyl substituents on sulfur, and the application of these ligands to Pd-catalyzed asymmetric allylic alkylation of indoles is reported. The sulfur substituent served as an effective stereocontrol element, and in the case of the 2-i-PrPh substituent on sulfur, the allylation products from an array of simple and substituted indoles were obtained with high enantioselectivity (up to 95% ee). 相似文献
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This paper reports a successful development of a group of efficient soluble polymer-supported chiral tartrate ligands by liquid-phase synthesis for Sharpless epoxidation of a variety of allylic alcohols through ligand diversity. The influence of substituent in chiral tartrate ligands on the enantioselectivities of the reaction was disclosed. Moderate chemical yields and good enantiomeric excesses were obtained by using soluble polymer-supported tartrate ester in the epoxidation of allylic alcohols with Ti(O-i-Pr)(4)/tert-butyl hydroperoxide. 相似文献
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《Tetrahedron: Asymmetry》2006,17(22):3067-3069
Cyclopropanation of 3,3-diaryl-2-propen-1-ols 1 with Et2Zn and CH2I2 proceeded in the presence of a catalytic amount of (S)-2-(methanesulfonyl)amino-1-(p-toluenesulfonyl)amino-3-phenylpropane 2 to afford the corresponding cyclopropylmethanols with 20–76% ee. (+)-2,2-Diphenylcyclopropylmethanol 3a (76% ee) was oxidized with IBX in DMSO, followed by NaClO2, H2O2, and NaH2PO4 in MeCN–H2O to give the corresponding acid 5a, which was converted with ethylenediamine, in the presence of PyBOP and Et3N in CH2Cl2, to the amide 6a in quantitative overall yield from 3a. Amide 6a was cyclized at 160 °C under reduced pressure (2 mmHg) to afford (R)-(+)-cibenzoline in 55% yield. 相似文献
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Matsuo J Kozai T Nishikawa O Hattori Y Ishibashi H 《The Journal of organic chemistry》2008,73(17):6902-6904
Oxazaborolidine-catalyzed enantioselective reduction of alpha-methylene ketones was efficiently carried out by using borane-diethylaniline as a stoichiometric reducing agent. The combination of this method and subsequent hydrogenation of thus-formed allylic alcohol improved stereoselectivity in the reduction of 24-oxocholesteryl ester to 24-(R)-hydroxycholesteryl ester. 相似文献
10.
A practical one-pot method has been developed for preparing enantioenriched secondary allylic alcohols starting from terminal alkynes and aldehydes. Hydroboration of terminal alkynes with dicyclohexylborane and subsequent reaction of the resulting alkenylboron reagents with aldehydes in the presence of a catalytic amount (5 mol %) of 3-(3,5-diphenylphenyl)-H(8)-BINOL and excess titanium tetraisopropoxide afforded the corresponding allylic alcohols in high enantioselectivities up to 94% ee. 相似文献
11.
A highly enantioselective method for catalytic reductive coupling of alkynes and aldehydes is described. Allylic alcohols are afforded with complete E/Z selectivity, generally >95:5 regioselectivity, and in up to 96% ee. In conjunction with ozonolysis, this process is complementary to existing methods of enantioselective alpha-hydroxy ketone synthesis. 相似文献
12.
Miura T Nakashima K Tada N Itoh A 《Chemical communications (Cambridge, England)》2011,47(6):1875-1877
Oxidation of alcohols in the presence of a catalytic amount of fluorous IBX and Oxone as a co-oxidant resulted in the corresponding carbonyl compounds in good to high yields. The fluorous IBX is readily recovered as insoluble fluorous IBA from the reaction mixture by simple filtration, and can be reused without significant loss of the catalytic activity. 相似文献
13.
《Tetrahedron: Asymmetry》1999,10(3):543-550
Eight new chiral oxazolinylpyridines were prepared and assessed in the enantioselective palladium-catalyzed allylic substitution of 1,3-diphenylprop-2-enyl acetate with dimethyl malonate. Catalytic activity and enantioselectivity were found to be highly dependent upon the steric requirement of the substituent on the pyridine ring: enantioselectivity up to 92% has been obtained. 相似文献
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In this perspective we give an overview of enantioselective C-H activation at allylic sites by means of rhodium(II)-stabilized donor-acceptor-substituted carbenoids. This methodology has been proven to be both an equivalent to established asymmetric reaction sequences and a new synthetic approach with no established counterpart in organic synthesis. 相似文献
18.
Jasquer A. Sehnem Priscila Milani Vanessa Nascimento Leandro H. Andrade Luciano Dorneles Antonio L. Braga 《Tetrahedron: Asymmetry》2010,21(8):997-1003
N-Trifluoracyl β-chalcogeno amides and N-perfluoracyl β-thio amide ligands were prepared by a simple and efficient reaction sequence. These new ligands were evaluated in palladium-catalyzed alkylation of rac-(E)-1,3-diphenyl-2-propenyl acetate in the presence of dimethyl malonate and an enantioselectivity of up to 99% was obtained. After catalysis, the fluorous ligand can be easily recovered by liquid–liquid extraction and reused without loss in the activity. 相似文献
19.
《Tetrahedron: Asymmetry》2001,12(16):2323-2329
A new class of diamino diols was evaluated as catalytic ligands in the enantioselective borane reduction of aromatic ketones and the enantioselective ethylation of arylaldehydes with diethylzinc. By variation of the substitution pattern on the ketone, e.e.s of up to 94% could be obtained by in situ borane reduction using 0.025 equiv. of the ligand at 35°C in THF. N,N,N′,N′-Tetramethyldiamino diol and N,N′-dialkyl diamino diol were used as promoters for the enantioselective addition of diethylzinc reagent to the arylaldehyde, where use of 0.1 equiv. of N,N,N′,N′-tetramethyl diamino diol as catalyst in the addition of diethylzinc to arylaldehyde achieved e.e.s of up to 98%. 相似文献