- Catalytic enantioselective oxidative cross-coupling of benzylic ethers with aldehydes
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The first one-pot enantioselective oxidative coupling of cyclic benzylic ethers with aldehydes has been developed. A variety of benzylic ethers were transformed into the corresponding oxygen heterocycles with high enantioselectivity. Mechanistic experiments were conducted to determine the nature of the reaction intermediates. The application of this strategy to coupling reactions with other nucleophiles besides aldehydes was also explored. In one go: The first one-pot enantioselective oxidative coupling of cyclic benzylic ethers with aldehydes has been developed. A variety of benzylic ethers could be functionalized with this method, and the corresponding oxygen heterocycles were obtained with high enantioselectivity.
- Meng, Zhilin,Sun, Shutao,Yuan, Huiqing,Lou, Hongxiang,Liu, Lei
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p. 543 - 547
(2014/01/23)
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- Preparation of Hydroperoxides by N-Hydroxyphthalimide-Catalyzed Aerobic Oxidation of Alkylbenzenes and Hydroaromatic Compounds and Its Application
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An efficient approach to phenols and aldehydes through the formation of hydroperoxides from alkylbenzenes was successfully achieved by aerobic oxidation using N-hydroxyphthalimide (NHPI) as a catalyst. The oxidation of various alkylbenzenes with dioxygen by NHPI followed by treatment with a Lewis acid or triphenylphosphine led to phenols or aldehydes, respectively, in good yields. For example, the aerobic oxidation of cumene in the presence of a catalytic amount of NHPI at 75°C and subsequent treatment with H2SO4 gave phenol in 77% yield. 1,4-Dihydroxybenzene (61%) and 4-isopropylphenol (33%) were obtained from 1,4-diisopropylbenzene. On the other hand, dibenzyl ether was converted into phenol or benzaldehyde upon treatment of the resulting hydroperoxide with InCl3 or PPh3, respectively.
- Fukuda, Osamu,Sakaguchi, Satoshi,Ishii, Yasutaka
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p. 809 - 813
(2007/10/03)
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- Cobalt-Catalyzed Partial Oxidation of Olefins and Ethers Using Molecular Oxygen
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Co(acac)3 catalyzes the aerobic oxidation of vinyl aromatic compounds ArCH=CH2 with formation of ArCO2H and ArCHO, and also the aerobic oxidation of cyclic ethers with formation of the corresponding lactones.
- Reetz, Manfred T.,Toellner, Karl
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p. 9461 - 9464
(2007/10/02)
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- Carbenes and the O-H Bond: Hydroxyalkyl-Substituted Arylcarbenes
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carbene (4), phenylcarbene (19), and carbene (30) have been generated by photolysis of tosylhydrazone or diazo precursors in protic solvents.These carbenes give cyclic ethers (7, 18, 33) competitively with insertion into O-H bonds of the solvent.For comparison, the analogous benzyl cations (9, 17, 31) have been generated by solvolysis or dediazoniation.The cations are more sensitive to structural variation than their carbenic counterparts: 9 does not undergo intramolecular nucleophilic substitution, in contrast to 17 and 31.These observations are explicable in terms of high barriers for rotation about aryl-cation bonds, as compared with low barriers for rotation about aryl-carbene bonds.Two major effects of the solvent (ROH) and of the base (RONa) on product formation may be distinguished: (i) protonation of the carbene (or of its precursors) in the more acidic media leads to predominantly cationic processes; (ii) deprotonation of the OH group under strongly basic conditions enhances the nucleophilicity of the oxygen, and also facilitates insertion into the α-C-H bonds of 30.
- Kirmse, Wolfgang,Kund, Klaus
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p. 2325 - 2332
(2007/10/02)
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