- C?O coupling of Malonyl Peroxides with Enol Ethers via [5+2] Cycloaddition: Non-Rubottom Oxidation
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Malonyl peroxides act both as oxidants and reagents for C?O coupling in reactions with methyl and silyl enol ethers. In the proposed conditions, the oxidative C?O coupling of malonyl peroxides with enol ethers selectively proceeds, bypassing the traditional Rubottom hydroxylation of enol ethers by peroxides. It was observed that the oxidative [5+2] cycloaddition of malonyl peroxides and enol ethers is the key stage of the discovered process. Oxidative C?O coupling of silyl enol ethers leads to the formation of α-acyloxyketones with a free carboxylic acid group. A specially developed preparative one-pot procedure transforms ketones via silyl enol ethers formation and the following coupling into α-acyloxyketones with yields 35–88%. The acid-catalyzed coupling with methyl enol ethers gives remarkable products while retaining the easily oxidizable enol fragment. Furthermore, these molecules contain a free carboxylic acid group, thus these nontrivial products contain two usually incompatible acid and enol ether groups. (Figure presented.).
- Vil', Vera A.,Gorlov, Evgenii S.,Bityukov, Oleg V.,Barsegyan, Yana A.,Romanova, Yulia E.,Merkulova, Valentina M.,Terent'ev, Alexander O.
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supporting information
p. 3173 - 3181
(2019/05/15)
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- Iodine promoted α-hydroxylation of ketones
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A novel method for α-hydroxylation of ketones using substoichiometric amount of iodine under metal-free conditions is described. This method has been successfully employed in synthesizing a variety of heterocyclic compounds, which are useful precursors. α-Hydroxylation of diketones and triketones are illustrated. This strategy provides a novel, efficient, mild and inexpensive method for α-hydroxylation of aryl ketones using a sub-stoichiometric amount of molecular iodine.
- Siddaraju, Yogesh,Prabhu, Kandikere Ramaiah
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p. 6749 - 6753
(2015/06/25)
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- Oxazoles for click chemistry II: Synthesis of extended heterocyclic scaffolds
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Abstract New routes to 2,4,5-trisubstituted oxazoles were established whereby the substitution pattern was established by the structure of the starting nonsymmetrical acyloins. 2-Chloromethyl-4, 5-disubstituted oxazoles were prepared by refinements of an earlier described process whereby chloroacetyl esters of symmetrical and nonsymmetrical acyloins were cyclized using an ammonium acetate/acetic acid protocol. After substitution is effected, the azide moiety is then installed by substitution under mild conditions. While dibrominated and iodinated phenyloxazoles are required for further synthetic elaboration, the cyclization reaction was found to be very sensitive to the relative positions of the halogens in the starting materials.
- Patil, Pravin C.,Luzzio, Frederick A.,Demuth, Donald R.
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supporting information
p. 3039 - 3041
(2015/05/27)
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- Chemoselective and repetitive intermolecular cross-acyloin condensation reactions between a variety of aromatic and aliphatic aldehydes using a robust N-heterocyclic carbene catalyst
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We found that chemoselectivity of the crossed acyloin product is controlled by the adjustment of the aromatic aldehyde/aliphatic aldehyde ratio. Moreover, we observed the persistent catalytic activity of the homogeneous NHC catalyst in a solution due to N
- Jin, Ming Yu,Kim, Sun Min,Mao, Hui,Ryu, Do Hyun,Song, Choong Eui,Yang, Jung Woon
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supporting information
p. 1547 - 1550
(2014/03/21)
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- Multistep oxidase-lyase reactions: Synthesis of optically active 2-hydroxyketones by using biobased aliphatic alcohols
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Enzymatic multistep reactions are presently an important research field, from which integrated and efficient synthetic protocols can be created, accompanied by a diminished waste formation (avoiding downstream units operations). This article explores the benzaldehyde lyase (BAL) catalyzed crossed carboligation of benzaldehyde with different aliphatic aldehydes to afford optically active α-hydroxyketones. To this end, different biobased aliphatic alcohols were insitu oxidized to aldehydes by oxidase from Hansenula sp. and subsequently carboligated with benzaldehyde by BAL in the same reactor system. For short nonbranched aliphatic alcohols, moderate to high conversions in carboligations (15-99%) with excellent enantioselectivities (98-99%, R), were achieved. Both enzymes also exhibited activities at high concentrations of benzaldehyde (up to 200mM) and with butanol as cosolvent, albeit at the cost of lower conversions, presumably owing to kinetic reasons. After needed optimization of the biocatalyst (e.g., through genetic evolution, whole-cell setup) and the process setup (e.g., stepwise addition of substrates, reaction time), the herein reported concept might provide promising entries in the field of asymmetric synthesis, delivering useful building blocks starting from biobased materials, and in an integrative manner.
- Perez-Sanchez, Maria,Mueller, Christoph R.,DominguezdeMaria, Pablo
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p. 2512 - 2516
(2013/08/23)
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- Polymer-supported synthesis of α- and β-hydroxyketones through the formation of 1,3-dithiane intermediates
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The synthesis of polymer-supported 2-monosubstituted 1,3-dithianes from soluble copolymers bearing 1,3-propanedithiol groups, their lithiation, reactions with electrophiles such as aldehydes, ketones, α,β- unsaturated ketones and oxiranes, and cleavage of
- Bertini, Vincenzo,Lucchesini, Francesco,Pocci, Marco,Alfei, Silvana,Idini, Barbara
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body text
p. 1141 - 1144
(2009/04/06)
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- Asymmetric oxidation of enol phosphates to α-hydroxy ketones by?(salen)manganese(III) complex. Effects of the substitution pattern of enol phosphates on the stereochemistry of oxygen?transfer
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This paper presents a study of enantioselective catalytic oxidation of a variety of differently substituted, cyclic (E) and acyclic (Z)-enol phosphates. The asymmetric oxidation of acyclic (Z)-enol phosphates containing alkoxy substituents in the phosphate group 2a, c, e-g, i, and j and Z-configured enol phosphates containing aryloxy substituents in the phosphate group 2b, d, and h afforded optically active α-hydroxy ketones 4a-j of opposite configuration with good to high enantioselectivity. The influence of electronic and steric effects of the enol phosphate substituents on the stereoselectivity of oxidation was studied.
- Koprowski, Marek,?uczak, Jerzy,Krawczyk, Ewa
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p. 12363 - 12374
(2007/10/03)
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- α-Hydroxy ketones in high enantiomeric purity from asymmetric oxidation of enol phosphates with (salen) manganese(III) complex
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Optically active α-hydroxy ketones 4 have been prepared in high enantioselectivity by the catalytic, enantioselective oxidation of easily available and stable (E)-enol phosphates 2 by (salen) Mn(III) complex.
- Krawczyk, Ewa,Koprowski, Marek,Skowronska, Aleksandra,Luczak, Jerzy
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p. 2599 - 2602
(2007/10/03)
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- Asymmetric reduction of α-keto esters and α-diketones with a bakers' yeast keto ester reductase
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Optically pure α-hydroxy esters and α-hydroxy ketones have been synthesized by the reduction of the corresponding ketones with a keto ester reductase isolated from bakers' yeast (YKER-I). The reduction of α-keto esters affords the corresponding (S)- or (R)-hydroxy esters selectively, where the stereochemical course depends on the chain length of the alkyl substituent on the carbonyl group. An α-keto short alkanoic ester affords the corresponding (S)-hydroxy ester, whereas a long alkanoate yields the corresponding (R)-hydroxy ester. The reduction of α-diketones affords the corresponding (S)-2-hydroxy ketones regio- and stereoselectively.
- Kawai, Yasushi,Hida, Kouichi,Tsujimoto, Munekazu,Kondo, Shin-Ichi,Kitano, Kazutada,Nakamura, Kaoru,Ohno, Atsuyoshi
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- A New Type of P-C and C-C Bond Cleavage Reactions in α-Trimethylsilyloxy-β-oxo Phosphonates and α-Ethoxy-β-oxo Phosphonates. The Synthesis of Unsymmetrical α-Hydroxy Ketones Utilizing 1:1 Carbonyl Adducts of Diethyl Trimethylsilyl Phosphite with Benzaldehyde
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α-Lithiated diethyl α-(trimethylsilyloxy)benzylphosphonate underwent facile acylation with various acylating agents to afford the corresponding α-acylated products in good yields.On treatment with the α-acylated products with 1 M NaOH-EtOH (1:1, v/v) the P-C bond was cleaved with elimination of diethyl phosphate to give α-hydroxy ketones predominantly.On the other hand, when diethyl α-acyl-α-ethoxybenzylphosphonates were treated under the same conditions, they were rather stable and recovered.However, the prolonged alkaline treatment or the use of 4 M NaOH-EtOH (1:1 v/v) resulted in the C-C bond cleavage giving carboxylic acids and diethyl α-ethoxybenzylphosphonate in quantitative yields, respectively.The mechanisms of the above two reactions were proposed and discussed in connection with the Perkow reaction and related reactions.
- Sekine, Mitsuo,Nakajima, Masashi,Hata, Tsujiaki
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p. 218 - 223
(2007/10/02)
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- BETA-ADRENERGIC BLOCKING AGENTS IN THE 1,2,3-THIADIAZOLE SERIES
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Novel 4-2,3 or 4(3-amino-2-hydroxypropoxy) phenyl!-and 5-2, 3 or 4(3-amino-2-hydroxypropoxy) phenyl!-1,2,3-thiadiazole derivatives which may be further substituted at the C-5 or C-4 position of the thiadiazole ring, respectively, by a lower alkyl, phenyl, trifluoromethyl, carboxy, alkoxycarbonyl, cyano or an aminocarbonyl group, and the pharmaceutically acceptable acid addition salts thereof and processes for the production of such compounds; 4-4(3-t-butylamino-2-hydroxypropoxy) phenyl!-1,2,3-thiadiazole and 5-4(3-t-butylamino-2-hydroxypropoxy) phenyl!-1,2,3-thiadiazole are representative of the class. These compounds possess cardiovascular activity and are useful for the treatment of abnormal heart conditions in mammals.
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