- 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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- Continuous Flow Acylation of (Hetero)aryllithiums with Polyfunctional N,N-Dimethylamides and Tetramethylurea in Toluene
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The continuous flow reaction of various aryl or heteroaryl bromides in toluene in the presence of THF (1.0 equiv) with sec-BuLi (1.1 equiv) provided at 25 °C within 40 sec the corresponding aryllithiums which were acylated with various functionalized N,N-
- Djukanovic, Dimitrije,Filipponi, Paolo,Heinz, Benjamin,Knochel, Paul,Mandrelli, Francesca,Martin, Benjamin,Mostarda, Serena
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supporting information
p. 13977 - 13981
(2021/09/13)
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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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- Flexible stereoselective functionalizations of ketones through umpolung with hypervalent iodine reagents
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The functionalization of carbonyl compounds in the α-position has gathered much attention as a synthetic route because of the wide biological importance of such products. Through polarity reversal, or "umpolung", we show here that typical nucleophiles, such as oxygen, nitrogen, and even carbon nucleophiles, can be used for addition reactions after tethering them to enol ethers. Our findings allow novel retrosynthetic planning and rapid assembly of structures previously accessible only by multistep sequences. A Nu approach: An efficient α-functionalization of ketones with a range of simple and useful nucleophiles is possible by using hypervalent iodine reagents (see scheme; Nu′ can be the Nu itself or a protected form of this nucleophile group).
- Mizar, Pushpak,Wirth, Thomas
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supporting information
p. 5993 - 5997
(2014/06/10)
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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 iodination of carbonyl compounds using ammonium iodide and oxone
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A simple, efficient, mild, and regioselective method for oxyiodination of carbonyl compounds has been reported by using NH4I as the source of iodine and Oxone as an oxidant. Various carbonyl compounds such as aralkyl ketones, aliphatic ketones (acyclic and cyclic), and β-keto esters proceeded to the respective α-monoiodinated products in moderate to excellent yields. Unsymmetrical aliphatic ketones reacted smoothly yielding a mixture of 1-iodo and 3-iodo ketones with the predominant formation of 1-iodoproduct.
- Marri, Mahender Reddy,MacHarla, Arun Kumar,Peraka, Swamy,Nama, Narender
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supporting information; experimental part
p. 6554 - 6559
(2012/01/02)
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- Direct conversion of aromatic ketones to arenecarboxylic esters via carbon-carbon bond-cleavage reactions
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Aromatic methyl ketones, ss-keto esters, and trifluoromethyl-l,3- diketones can be directly converted to arene-carboxylic esters via carbon-carbon bond cleavage of pyridinium iodide intermediates in the presence of copper(II) oxide, iodine, pyridine, and potassium carbonate in alcoholic media. The advantages of the present method in terms of good yields, mild reaction conditions, and inexpensive reagents should make this protocol a valuable alternative to the existing methods.
- Yin, Guodong,Gao, Meng,Wang, Zihua,Wu, Yandong,Wu, Anxin
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scheme or table
p. 369 - 372
(2009/04/07)
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- Decarbonylative diarylation of α-methoxyacetic acid yielding diarylmethanes mediated by Lewis acid and trifluoroacetic anhydride
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Reaction of α-methoxyacetic acid with aromatic compounds in the presence of trifluoroacetic anhydride and Lewis acid has been found to give diarylmethanes. Some of the intermediates in this transformation have been identified via direct observation by 1H and 13CNMR spectroscopy. The reaction route has been clarified as follows: a mixed acid anhydride is formed from α-methoxyacetic acid and trifluoroacetic anhydride, which gives a hemiacylal type intermediate via decarbonylation followed by successive double electrophilic aromatic substitutions yielding diarylmethanes. Copyright
- Jobashi, Takashi,Hino, Tetsuo,Maeyama, Katsuya,Ozaki, Hiroyuki,Ogino, Kenji,Yonezawa, Noriyuki
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p. 860 - 861
(2007/10/03)
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- A new and mild heterogeneous catalytic decomposition of α-diazo carbonyl compounds using montmorillonite or zeolite
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A very mild method of decomposition of various α-diazo carbonyl compounds 1 in the presence of environmentally attractive solid acids such as montmorillonite K-10 or zeolite H-Y in a heterogeneous manner to furnish α-hydroxy/alkoxy ketones in very good yield is reported. Interestingly, novel bicycloalkane-1,3-diones and 3-furanones were obtained as unusual products in the case of aliphatic/alicyclic α-diazo carbonyl compounds.
- Muthusamy, Sengodagounder,Babu, Srinivasarao Arulananda,Gunanathan, Chidambaram,Jasra, Raksh Vir
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p. 407 - 410
(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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- Reactions of diazoalkanes with molybdenum peroxide
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The reactions of diazoalkanes with MoO5·HMPA·H2O caused both oxidation into carbonyl compounds and metal carbenoid insertion reaction with methanol to give methyl alkyl ethers. These reaction paths are affected by the substituent of diazoalkanes.
- Kawasaki, Tomomi,Hoshi, Ryuichi,Yamamoto, Toshihiko,Satoh, Kazue,Sakamoto, Masanori
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p. 565 - 572
(2007/10/03)
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- Structural requirements for decarbonylative α,α-diarylation reaction of 2-methoxyalkanoic acids in phosphorus pentoxide-methanesulfonic acid mixture yielding 1,1-diarylalkane homologs
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2-Methoxyalkanoic acids were found to undergo consecutive decarbonylative α,α-diarylation in P2O5-MsOH instead of Friedel-Crafts type arylation on the carbonyl carbon. The influence of the substituents of the arenes and the carboxylic acids in this reaction was elucidated based on the reaction yields. The reaction behavior was found to be primarily governed by the electron-withdrawing/releasing property of the α-substituents on the carboxylic acids as well as the positive species-accepting ability of the arenes. The steric hindrance was shown to participate in determining the reaction feasibility as a secondary factor.
- Yonezawa, Noriyuki,Hino, Tetsuo,Tokita, Yoshimi,Matsuda, Kazuhisa,Ikeda, Tomiki
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p. 14287 - 14296
(2007/10/03)
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- Baker's yeast-mediated reduction of α-hydroxy ketones and derivatives: The steric course of the biotransformation
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The results from the baker's yeast-mediated reduction of the acetates 3a- d and the methyl ethers 5a-d were compared with the same biotransformation which converts the α-hydroxy ketones 1a-d into the (R)-diols 2a-d (90- 98%ee); the acetates 3a-d afford the (S)-monoacetates 4a-d (72-94% ee) and the methyl ethers 5a-d are reduced to the (R)-monoethers 6a-d (64-76% ee).
- Ferraboschi, Patrizia,Grisenti, Paride,Manzocchi, Ada,Santaniello, Enzo
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p. 10539 - 10548
(2007/10/02)
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- COMPLEXATION OF A FLUORESCENT ANTHOCYANIN WITH PURINES AND POLYPHENOLS
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It is demonstrated that the synthetic anthocyanin 7-hydroxy-3,4'-dimethoxyflavylium chloride associates with copigments in a manner which mimics that of natural anthocyanins.When studying copigmentation, 7-hydroxy-3,4'-dimethoxyflavylium chloride offers several advantages over its natural homologues.Firstly, it is easy to prepare pure.Secondly, its unexpected strong fluorescence opens up a new field in copigmentation studies.Finally, being sufficiently water-soluble, its complexation can also be investigated by means of 1H NMR spectroscopy.Copigments investigated are : chlorogenic acid, gallic acid, caffeine, adenosine 5'-monophosphate and adenosine 5'-triphosphate. Key Word Index: Anthocyanin complexation; purines; polyphenols; UV-visible, fluorescence and 1H NMR spectroscopy.
- Wigand, Marie Claude,Dangles, Olivier,Brouillard, Raymond
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p. 4317 - 4324
(2007/10/02)
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- A Study of Rearrangement of some 1,3-Dimethoxyalkan-2-ones
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1,3-Dialkoxyacetones, 1-alkyl- and 1-(substituted phenyl)-, 1-alkanoyl-1,3-dimethoxyacetones, and methyl 2,4-dimethoxyacetoacetate were shown to undergo acid-catalysed rearrangement to give respectively methylglyoxal dialkyl acetals, 3-substituted methylglyoxal dimethyl acetals, 5-alkyl-3-methoxy- and 4,5-dimethoxyfuran-2(5H)-ones. 1-(Substituted aroyl)-1,3-dimethoxyacetones underwent only scission to give substituted ω-methoxyacetophenones.Methyl 2-alkyl-2,4-dimethoxyacetoacetates, 3- and 1-methoxy-, and 1,5-dimethoxypentane-2,4-diones were not affected by similaracid treatment except for the fact that they suffered some limited C-C bond scissions.Implications related to rearrangement mechanisms are discussed.
- Yu, Yin,Chen, Guo-qiang,Zhu, Jun,Zhang, Xu-sheng,Chen, Shu-xin,et al.
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p. 2239 - 2243
(2007/10/02)
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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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- 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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