- Intermolecular C-O Bond Formation with Alkoxyl Radicals: Photoredox-Catalyzed α-Alkoxylation of Carbonyl Compounds
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Due to the high reactivity of alkoxyl (RO·) radicals and their propensity to easily undergo β-scission or Hydrogen Atom Transfer (HAT) reactions, intermolecular alkoxylations involving RO· radicals are barely described. We report herein for the first time the efficient intermolecular trapping of alkoxyl radicals by silyl enol ethers. This photoredox-mediated protocol enables the introduction of both structurally simple and more complex alkoxy groups into a wide range of ketones and amides.
- Banoun, Camille,Bourdreux, Flavien,Magnier, Emmanuel,Dagousset, Guillaume
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supporting information
p. 8926 - 8930
(2021/11/17)
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- Tandem Acid/Pd-Catalyzed Reductive Rearrangement of Glycol Derivatives
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Herein, we describe the acid/Pd-tandem-catalyzed transformation of glycol derivatives into terminal formic esters. Mechanistic investigations show that the substrate undergoes rearrangement to an aldehyde under [1,2] hydrogen migration and cleavage of an oxygen-based leaving group. The leaving group is trapped as its formic ester, and the aldehyde is reduced and subsequently esterified to a formate. Whereas the rearrangement to the aldehyde is catalyzed by sulfonic acids, the reduction step requires a unique catalyst system comprising a PdII or Pd0 precursor in loadings as low as 0.75 mol % and α,α′-bis(di-tert-butylphosphino)-o-xylene as ligand. The reduction step makes use of formic acid as an easy-to-handle transfer reductant. The substrate scope of the transformation encompasses both aromatic and aliphatic substrates and a variety of leaving groups.
- Ciszek, Benjamin,Fleischer, Ivana,Kathe, Prasad,Schmidt, Tanno A.
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supporting information
p. 3641 - 3646
(2020/03/25)
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- Direct Synthesis of α-Alkoxy Ketones by Oxidative C–O Bond Formation
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A convenient method to prepare α-alkoxy ketones has been developed by oxidative coupling of aryl methyl ketones and alcohols. With aqueous tert-butyl hydroperoxide (6.0 equiv.) as the oxidant, tetrabutylammonium iodide (20 mol-%) as the catalyst, and TsNHNH2(1.0 equiv.) as the additive, ketones underwent direct alkoxylation to give α-methoxy or α-ethoxy ketones in moderate to good yields.
- Yu, Hui,Xu, Yilan,Fang, Yan,Dong, Rui
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p. 5257 - 5262
(2016/11/13)
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- Highly efficient synthesis of functionalized α-oxyketones: Via Weinreb amides homologation with α-oxygenated organolithiums
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An efficient, chemoselective homologation of Weinreb amides to the corresponding variously substituted α-oxyketones has been developed via the addition of lithiated α-oxygenated species. This one-step, experimentally easy, high yielding protocol is amenable not only for accessing simple α-oxyketones but also for more complex substituted ones ranging from primary and secondary alkyl-type to aromatic ones. Full delivery of the stereochemical information contained in the starting materials is observed through both the employment of enantioenriched Weinreb amides and optically active organolithium species.
- Pace, Vittorio,Murgia, Irene,Westermayer, Sophie,Langer, Thierry,Holzer, Wolfgang
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supporting information
p. 7584 - 7587
(2016/07/06)
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- Experimental study on the reaction pathway of α-haloacetophenones with NaOMe: Examination of bifurcation mechanism
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The reaction of PhCOCH2Br and NaOMe in MeOH gave PhCOCH 2OH as the major product and PhCOCH2OMe as the minor product. Substituent effects on the reactivity and product selectivity revealed that an electron-withdrawing substituent on the phenyl ring enhanced the overall reactivity and gave more alcohol than ether. It was indicated that the alcohol was formed via carbonyl addition-epoxidation, whereas the ether was formed by direct substitution. Substituent effects on the reaction rates, as well as the effects of NaOMe concentration on the rate and product ratio for both reactions of PhCOCH2Br and PhCOCH2CI are in line with the mechanism that the alcohol and ether products were formed via two independent and concurrent routes, carbonyl addition and a-carbon attack, respectively, and thus the reaction mechanism could be different from the bifurcation mechanism previously predicted for the reaction of PhCOCH2Br by a simulation study in the gas phase.
- Tagawa, Kohei,Sasagawa, Keita,Wakisaka, Ken,Monjiyama, Shunsuke,Katayama, Mika,Yamataka, Hiroshi
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p. 119 - 126
(2014/02/14)
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- Oxidative rearrangements of arylalkanones with 1H-1-hydroxy-5-methyl-1,2,3-benziodoxathiole 3,3-dioxide, a 'green' analog of Koser's reagent
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Previous methods for the conversion of arylalkanones to alkyl 2-arylesters by oxidative rearrangement utilized reagents which either produced toxic metal salts or halogenated organics as by-products. In this report, 1H-1-hydroxy-5-methyl-1,2,3-benziodoxathiole 3,3-dioxide (HMBI) is used to effect this useful transformation, where the reduced iodine reagent is water-soluble and readily recycled.
- Justik, Michael W.
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p. 3003 - 3007
(2008/02/06)
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- 2,4-DIAMINOQUINAZOLINES FOR SPINAL MUSCULAR ATROPHY
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2,4-Diaminoquinazolines of formulae I-IV and VI (I, II, III, IV and VI) are useful for treating spinal muscular atrophy (SMA).
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Page/Page column 74
(2010/02/15)
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- Scandium triflate catalyzed diazocarbonyl insertions into heteroatom- hydrogen bonds
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Scandium triflate is an efficient catalyst for diazocarbonyl insertion reactions into O-H, S-H and carbamate N-H bonds. The O-H and S-H insertion reactions proceed at ambient temperature and selective O-H insertion is possible in the presence of a carbama
- Pansare, Sunil V.,Jain, Rajendra P.,Bhattacharyya, Annyt
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p. 5255 - 5258
(2007/10/03)
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- Reaction of phosphonium ylides and aromatic nitriles under lewis acid conditions: An easy access to aryl-substituted α-methoxyacetophenones
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In the presence of lithium chloride, as Lewis acid, the reaction of methoxymethyltriphenylphosphonium ylide 1 with aromatic nitriles 2 as phenacyl cation equivalents gives access to the corresponding α- methoxyacetophenones 3 in good yields.
- Camuzat-Dedenis,Provot,Moskowitz,Mayrargue
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p. 1558 - 1560
(2007/10/03)
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- Metal-Metal Exchange of α-Metallo Ketones. Novel Formation of α-Acyl Anion and α-Keto Carbonium Ion Equivalents from (Aryl)phenacyl TlIII, PbIV, and HgII Systems
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The novel class of α-metallo ketones RCOCH2TlIIItolyl(OCOCF3) where R = phenyl, substituted phenyl, thienyl, pyridinyl, and tert-butyl have been synthesized and characterized by 1H NMR and 13C NMR.These compounds serve as anion equivalents in the TiCl4-mediated aldol condensation.Metal-metal exchange with iodosylbenzene or lead tetraacetate leads to α-nucleophilic substitution derived from the formal α-keto carbonium ion equivalent.The corresponding p-CH3OC6H4COCH2PbIVC6H4OCH3-p-(OCOCH3)2 and (p-CH3OC6H4COCH2)2HgII analogues were synthesized and shown to likewise behave as either enolate anion or α-keto carbonium ion equivalents upon metal-metal exchange with TiIV, PbIV, or IIII.The importance of this work is that the range of reactivity of α-metallo ketones may be selectively adjusted by metal-metal or metal-metalloid exchange.
- Moriarty, Robert M.,Penmasta, Raju,Prakash, Indra,Awasthi, Alok K.
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p. 1022 - 1025
(2007/10/02)
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- Hypervalent iodine oxidation of silyl enol ethers under Lewis acid conditions in methanol. A general route to α-methoxy ketones
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Hypervalent iodine oxidation of various silyl enol ethers (aromatic, heteroaromatic, aliphatic) using iodosobenzene-boron trifluoride etherate in methanol leads to α-methoxylation of ketones in high yields. The scope and mechanism of the reaction are discussed.
- Moriarty, Robert M.,Prakash, Om,Duncan, Michael P.,Vaid, Radhe K.,Musallam, Hikmat A.
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p. 150 - 153
(2007/10/02)
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- α-METHOXY KETONES BY THE REACTION OF TRIMETHYLSILYL ENOL ETHERS WITH LEAD TETRAACETATE IN METHANOL
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Trimethylsilyl enol ethers of acetophenone, 2-acetylthiophene and 2-acetylfuran react with lead tetraacetate in methanol at room temperature to give the α-methoxy ketones in good yields.
- Moriarty, Robert M.,Prakash, Indra,Penmasta, Raju
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p. 709 - 714
(2007/10/02)
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- SILVER ASSISTED REARRANGEMENT OF PRIMARY AND SECONDARY α-BROMO-ALKYLARYLKETONES
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The silver assisted rearrangement of primary and secondary α-bromo-alkylarylketones is reported for the first time.The influence of the acidity on the reaction selectivity is discussed.
- Giordano, Claudio,Castaldi, Graziano,Casagrande, Francesco,Abis, Luigi
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p. 1385 - 1386
(2007/10/02)
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