- Squaramide-catalyzed asymmetric intramolecular oxa-michael reaction of α,β-unsaturated carbonyls containing benzyl alcohol: Construction of chiral 1-substituted phthalans
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Organocatalytic enantioselective intramolecular oxa-Michael reactions of benzyl alcohol bearing α,β-unsaturated carbonyls as Michael acceptors are presented herein. Using cinchona squaramide-based organocatalyst, enones as well as α,βunsaturated esters containing benzyl alcohol provided their corresponding 1,3-dihydroisobenzofuranyl-1-methylene ketones and 1,3-dihydroisobenzofuranyl-1-methylene esters in excellent yields with high enantioselectivities. In addition, enantioenriched 1,3-dihydroisobenzofuranyl-1-methylene ketone could be obtained from the Wittig/oxa-Michael reaction cascade of 1,3-dihydro-2-benzofuran-1-ol.
- Son, Eun Chae,Kim, Seung Yeon,Kim, Sung-Gon
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p. 6826 - 6839
(2021/05/29)
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- Organocatalytic enantioselective synthesis of phthalans via Wittig/oxa-Michael cascade reaction
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An enantioselective synthetic method for 1-substituted phthalans has been developed. The organocatalytic reaction between 1,3-dihydro-2-benzofuran-1-ols and Wittig reagents using cinchona squaramide-based organocatalyst proceeded with sequential Wittig reaction followed by an enantioselective intramolecular oxa-Michael reaction, yielding enantioenriched phthalans with moderate to good enantioselectivities.
- Son, Eun Chae,No, Jaeeun,Kim, Sung-Gon
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p. 1473 - 1480
(2021/09/25)
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- 6-membered pseudocyclic IBX acids: Syntheses, X-ray structural characterizations, and oxidation reactivities in common organic solvents
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We designed and synthesized λ5-cyclic periodinanes 1 and 2, which are homologous to IBX (1-hydroxy-1-oxo-1H-1λ5- benzo[d][1,2]iodoxol-3-one) by one carbon, to thwart close packing of molecules in the crystal lattice to permit solubility in common organic solvents and to facilitate oxidations with enhanced reactivity. The X-ray crystal structures revealed that both 1 and 2 exist in the solid state as pseudocyclic (PC) acids, i.e., 1PC and 2PC, and that the molecules in the lattice are less weakly associated as compared to those in the parent IBX due to the twisting introduced via the sp3 benzylic carbon. Both 1PC and 2PC are found to dissolve in palpable amounts in DCM and acetonitrile to allow oxidation of a variety of alcohols and sulfides to carbonyl compounds and sulfoxides in a facile manner. The subtle differences in the sterics due to methyl and ethyl substituents in 1PC and 2PC are found to manifest in contrasting reactivities in that the oxidations of alcohols occur faster with 2PC, while those of sulfides to sulfoxides occur more rapidly with 1PC.
- Moorthy, Jarugu Narasimha,Senapati, Kalyan,Parida, Keshaba Nanda
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supporting information; experimental part
p. 8416 - 8421
(2011/03/20)
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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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- Method for production of aldehydes
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An ether of the following formula (2): (wherein Rais a hydrogen atom, a hydrocarbon group or a heterocyclic group, Rbis a hydrogen atom, a hydroxyl group or a substituted oxy group, and Rcis a hydrocarbon group or a heterocyclic group; Raand Rcmay be combined to form a ring with the adjacent carbon atom and oxygen atom) is reacted with nitrogen monoxide in the presence of a catalyst composed of an imide compound of the following formula (1): (wherein each of R1and R2is, identical to or different from each other, a hydrogen atom, a halogen atom, an alkyl group, an aryl group, a cycloalkyl group, a hydroxyl group, an alkoxy group, a carboxyl group, an alkoxycarbonyl group, or an acyl group; R1and R2may be combined to form a double bond, or an aromatic or nonaromatic ring; X is an oxygen atom or a hydroxyl group; and one or two N-substituted cyclic imido groups indicated in the formula (1) may further be formed on R1, R2, or on the double bond or aromatic or nonaromatic ring formed together by R1and R2) to give an aldehyde of the following formula (3): Ra—CHO??(3) (wherein Rahas the same meaning as defined above).
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- A New Approach for Oxygenation Using Nitric Oxide under the Influence of N-Hydroxyphthalimide
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An approach for partial oxygenation through a carbocation as an intermediate was successfully developed by using nitric oxide under the influence of N-hydroxyphthalimide. Thus, a variety of benzylic ethers were converted into the corresponding partially oxidized compounds, which are difficult to prepare by conventional methods, in high yields. For example, the reaction of phthalane with NO in the presence of a catalytic amount of NHPI at 60°C gave phthalaldehyde in 80% yield. The reaction was found to proceed through the formation of a hemiacetal, such as 1-hydroxyphthalane. In addition, 1,3-di-tert-butoxymethyl benzene afforded 1,3-benzenedicarbaldehyde in good yield. On the other hand, isochroman was converted into 1,1′-oxodiisochromane under these reaction conditions. The reaction of ethers with NO in the presence of a NHPI catalyst is thought to proceed via the formation of a carbocation as an intermediate. A possible reaction path was suggested.
- Eikawa, Masahiro,Sakaguchi, Satoshi,Ishii, Yasutaka
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p. 4676 - 4679
(2007/10/03)
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- Neighboring assistance of a hydroxyl group on manganese dioxide oxidation of benzyl alcohols to lactones
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o-Hydroxymethylbenzyl alcohol and o-hydroxyethylbenzyl alcohols have been converted to phthalide and dihydroisocoumarins, very easily and in high yields, by oxidation with non-activated manganese dioxide. In contrast, the reaction of o-hydroxypropylbenzyl alcohol stopped at the aldehyde level, and afforded only a small amount of the corresponding lactone under the same condition. This implies that the first oxidation product, a benzaldehyde, could be oxidized further via a hemiacetal, but the second oxidation to lactone is very much dependent on the ability of stable intramolecular hemiacetal formation, and not on the intermolecular mode at all.
- Endo, Katsuya,Takahashi, Hiroyasu,Aihara, Minako
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p. 589 - 615
(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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