- β-Diazocarbonyl Compounds: Synthesis and their Rh(II)-Catalyzed 1,3 C?H Insertions
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Herein, we describe the first electrophilic diazomethylation of ketone silyl enol ethers with diazomethyl-substituted hypervalent iodine reagents that gives access to unusual β-diazocarbonyl compounds. The potential of this unexplored class of diazo compounds for the development of new reactions was demonstrated by the discovery of a rare Rh-catalyzed intramolecular 1,3 C?H carbene insertion that led to complex cyclopropanes with excellent stereocontrol.
- Jiang, Liyin,Wang, Zhaofeng,Armstrong, Melanie,Suero, Marcos G.
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supporting information
p. 6177 - 6184
(2021/02/01)
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- Stereoselective Synthesis of Trisubstituted Vinylboronates from Ketone Enolates Triggered by 1,3-Metalate Rearrangement of Lithium Enolates
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An unprecedented stereoselective synthesis of trisubstituted vinylboronates is reported to proceed by direct borylation of lithium ketone enolates under transition-metal-free conditions. The stereospecific C?O borylation of lithium enolates was triggered by a carbonyl-induced 1,3-metalate rearrangement via a C-bound boron enolate. DFT calculations and control experiments revealed that the stereoselectivity is controlled by sterics. A variety of stereospecific trisubstituted vinylboronates, together with several tetrasubstituted vinylboronates, were conveniently synthesized with the newly developed methodology. Based on the transformation of stereospecific vinylboronate, a single isomer of Dienestrol was efficiently obtained.
- Hu, Yue,Sun, Wei,Zhang, Tao,Xu, Nuo,Xu, Jianeng,Lan, Yu,Liu, Chao
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supporting information
p. 15813 - 15818
(2019/10/28)
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- Organosilicon Reducing Reagents for Stereoselective Formations of Silyl Enol Ethers from α-Halo Carbonyl Compounds
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Salt-free stereoselective synthesis of silyl enol ethers was achieved by treating α-halo carbonyl compounds with 2,3,5,6-tetramethyl-1,4-bis(trimethylsilyl)-1,4-dihydropyrazine. In this reaction, easily removable trimethylsilyl halides and 2,3,5,6-tetramethylpyrazine were generated as the reaction byproducts. Due to the inertness of the reaction byproducts, we found a one-pot transformation of the in situ generated silyl enol ethers into various α-functionalized carbonyls by reaction with Togni-II reagent or aldehydes.
- Pramanik, Suman,Rej, Supriya,Kando, Shun,Tsurugi, Hayato,Mashima, Kazushi
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p. 2409 - 2417
(2018/02/23)
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- Activity of antifungal organobismuth(III) compounds derived from alkyl aryl Ketones against S. cerevisiae: Comparison with a heterocyclic bismuth scaffold consisting of a diphenyl sulfone
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A series of hypervalent organobismuth(III) compounds derived from alkyl aryl ketones [XBi(5-R′C6H3-2-COR)(Ar)] was synthesized to investigate the effect of the compounds' structural features on their antifungal activity against the yeast Saccharomyces cerevisiae. In contrast to bismuth heterocycles [XBi(5-RC6H3-2-SO 2C6H4-1′-)] derived from diphenyl sulfones, a systematic quantitative structure-activity relationship study was possible. The activity depended on the Ar group and increased for heavier X atoms, whereas lengthening the alkyl chain (R) or introducing a substituent (R′) reduced the activity. IBi(C6H4-2-COCH 3)(4-FC6H4) was the most active. Its activity was superior to that of the related acyclic analogues ClBi[C6H 4-2-CH2N(CH3)2](Ar) and ClBi(C 6H4-2-SO2 tert-Bu)(Ar) and also comparable to that of heterocyclic ClBi(C6H4-2-SO2C 6H4-1′-), which was the most active compound in our previous studies. Density function theory calculations suggested that hypervalent bismuthanes undergo nucleophilic addition with a biomolecule at the bismuth atom to give an intermediate ate complex. For higher antifungal activity, adjusting the lipophilicity-hydrophilicity balance, modeling the three-dimensional molecular structure around the bismuth atom, and stabilizing the ate complex appear to be more important than tuning the Lewis acidity at the bismuth atom.
- Murafuji, Toshihiro,Tomura, Mai,Ishiguro, Katsuya,Miyakawa, Isamu
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p. 11077 - 11095
(2014/10/15)
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- Direct use of esters in the Mukaiyama aldol reaction: A powerful and convenient alternative to aldehydes
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An indium triiodide catalyst promoted the direct transformation from esters to β-hydroxycarbonyl compounds using hydrosilanes and silyl enolates by a one-stage process. Various esters were applicable, and the high chemoselectivity of this system brings compatibility to many functional groups: alkenyl, alkynyl, chloro, and hydroxy.
- Inamoto, Yoshihiro,Nishimoto, Yoshihiro,Yasuda, Makoto,Baba, Akio
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supporting information; experimental part
p. 1168 - 1171
(2012/04/04)
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- Reaction of acylsilanes with α-sulfinyl carbanions: Regioselective synthesis of silyl enol ethers
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The reaction of acylsilanes with α-sulfinyl carbanions such as α-lithioalkyl sulfoxide is described. The reaction proceeds to give silyl enol ethers preferentially through the initial formation of the α-silyl alkoxide intermediates. In particular, the products derived from enolizable acylsilanes were the regio-defined silyl enol ethers that cannot be obtained by usual enolization of the corresponding unsymmetrical ketones with base.
- Honda, Mitsunori,Nakajima, Tadashi,Okada, Maiko,Yamaguchi, Keita,Suda, Mitsuhiro,Kunimoto, Ko-Ki,Segi, Masahito
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experimental part
p. 3740 - 3742
(2011/08/06)
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- Mechanistic studies on α-trifluoromethylation of ketones via silyl enol ethers and its application to other carbonyl compounds
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(Chemical Equation Presented) Synthesis of α-CF3 carbonyl compounds has been recognized to be difficult up to now because the polarization of CF3δ--Iδ+ is opposite to that of CH3δ+-Iδ-, and this makes it difficult to introduce CF3+ unit to enolates. We recently reported an effective R-trifluoromethylation of ketones by using Et 2Zn with Rh catalyst, but the mechanism has not fully been cleared. Now, we carried out the detailed mechanistic studies and found the involvement of a highly reactive alkylrhodium complex which derived from Et2Zn and RhCl(PPh3)3 in this α-trifluoromethylation. Furthermore, this α-trifluoromethylation was applied to other types of carbonyl compounds in good yields.
- Sato, Kazuyuki,Yuki, Takashi,Yamaguchi, Ryoji,Hamano, Tetsuya,Tarui, Atsushi,Omote, Masaaki,Kumadaki, Itsumaro,Ando, Akira
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supporting information; experimental part
p. 3815 - 3819
(2009/10/01)
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- Organic-inorganic hybrid polymer-encapsulated magnetic nanobead catalysts
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A new strategy for the encapsulation of magnetic nanobeads was developed by using the in situ self-assembly of an organic-inorganic hybrid polymer. The hybrid polymer of {[Cu-(bpy)(BF4)2(H2O) 2](bpy)}n (bpy = 4,4′-bipyridine) was constructed on the surface of amino-functionalized magnetic beads and the resulting hybrid-polymer-encapsulated beads were utilized as catalysts for the oxidation of silyl enolates to provide the corresponding α-hydroxy carbonyl compounds in high yield. After the completion of the reaction, the catalyst was readily recovered by magnetic separation and the recovered catalyst could be reused several times. Because the current method did not require complicated procedures for incorporating the catalyst onto the magnetic beads, the preparation and the application of various other types of organic-inorganic hybrid-polymer-coated magnetic beads could be possible.
- Arai, Takayoshi,Sato, Toru,Kanoh, Hirofumi,Kaneko, Katsumi,Oguma, Koichi,Yanagisawa, Akira
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p. 882 - 885
(2008/09/21)
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- Mild and efficient pentafluorophenylammonium triflate (PFPAT)-catalyzed C-acylations of enol silyl ethers or ketene silyl (Thio)acetals with acid chlorides
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A pentafluorophenylammonium triflate (PFPAT) catalyst (5 mol %) successfully promoted C-acylation of enol silyl ethers with acid chloride to produce various β-diketones (12 examples; 62-92% yield). Similarly, C-acylation of ketene silyl acetals or ketene
- Iida, Akira,Osada, Jun,Nagase, Ryohei,Misaki, Tomonori,Tanabe, Yoo
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p. 1859 - 1862
(2008/02/02)
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- Catalytic synthesis of α-hydroxy ketones using organic-inorganic hybrid polymer
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Oxidation of silyl enolates was found to be smoothly catalyzed by [Cu(bpy)(BF4)2(H2O)2(bpy)] n (bpy = 4,4′-bipyridine) under molecular oxygen, and provided the corresponding α-hydroxy carbonyl compounds in high yield. The insoluble organic-inorganic hybrid polymer was readily recovered by centrifugation after the completion of reaction, and the recovered catalyst could be reused. Copyright
- Arai, Takayoshi,Takasugi, Hitomi,Sato, Toru,Noguchi, Hiroshi,Kanoh, Hirofumi,Kaneko, Katsumi,Yanagisawa, Akira
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p. 1590 - 1591
(2007/10/03)
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- Investigations into the regioselective C-deuteration of acyclic and exocyclic enolates
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Results are reported on the regioselective C-deuteration of a series of related acyclic and exocyclic enolates derived from substituted aryl ketones. We comment on factors, such as the presence of additives and the structural nature of the enolate, that influence the observed C-deuteration and discuss the role of the deuterium donor. ( Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003).
- Eames, Jason,Coumbarides, Gregory S.,Suggate, Michael J.,Weerasooriya, Neluka
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p. 634 - 641
(2007/10/03)
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- A general and stereoselective method for synthesis of tri- and tetrasubstituted alkenes
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A convenient, general and stereoselective synthesis of trisubstituted alkenes and tetrasubstituted alkenes containing a cyanide function as well as trisubstituted episulphides have been elaborated. Methodology described for the preparation of these compounds is based on the corresponding readily available selenophosphates 1 and thiophosphates 2.
- Macia?giewicz,Dybowski,Skowrońska
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p. 6057 - 6066
(2007/10/03)
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- A novel approach to highly substituted enynes based on thiophosphates
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A novel approach to highly substituted enynes 5 via a new single and double carbon-carbon bond forming reaction involving interaction beetween readily available thiophosphates 1 and lithium acetytides is described.
- Macilgiewicz,Skowronska
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p. 1781 - 1782
(2007/10/03)
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- Mechanism of Arylation of Nucleophiles by Aryllead Triacetates. Part 2. Support for a Ligand Coupling Process and X-Ray Molecular Structure of (p-Methoxyphenyl)-α-methylphenacyllead(IV) Diacetate
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In the presence of boron trifluoride-diethyl ether complex p-methoxyphenyllead triacetate 4 and the propiophenone silyl enol ether 6 were found to undergo a rapid reaction to give (p-methoxyphenyl)-α-methylphenacyllead diacetate 9 in high yield.Analogous products, 5, 10 and 11, respectively, were formed when the silyl enol ethers of acetophenone, butyrophenone and isobutyrophenone were treated under the same conditions with aryllead compound 4.The diorganolead diacetates 9, 10 and 11 were relatively unstable, giving a number of products when heated at 60 deg C in chloroform.In each case there was significant elimination of Pb(OAc)2, with formation of the product of ligand coupling, the deoxybenzoin. α-Methylphenacyl(o-prop-2-enyloxy)phenyllead diacetate 21, which was produced to probe the mechanism of the coupling reaction, behaved similarly to compound 9, giving no dihydrobenzofuran derivatives.Therefore, it would appear that aryl free radicals are most probably not produced in these thermal reactions, and a ligand-coupling mechanism is proposed.
- Morgan, Jacqueline,Buys, Irmi,Hambley, Trevor W.,Pinhey, John T.
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p. 1677 - 1682
(2007/10/02)
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- ORGANOSELENIUM CHEMISTRY A STUDY OF INTERMEDIATES IN THE FRAGMENTATION OF ALIPHATIC KETOSELENOXIDES. CHARACTERIZATION OF SELENOXIDES, SELENENAMIDES AND SELENOLSELENINATES BY (1)H-, (13)C- AND (77)Se-NMR
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A series of β-ketoselenenic acids was generated at low temperature (-20 deg C to -50 deg C) by selenoxide syn elimination of appropriate selenoxides (13-ox, 16-ox, 35-ox, 38-ox, and 39-ox).No evidence for the buildup of significant concentrations of selenenic acid was obtained.A selenolseleninate (15, 2,2'-diseleno-bis(1-phenyl-2-methyl-1-propanone)-Se-oxide) was detected as an intermediate in the decomposition of 13-ox and 16-ox.This compound, which is stable in solution below -50 deg C was characterized by NMR spectroscopy ( (1)H, (13)C, (77)Se ) and by its thermal decomposition and reactions with phosphite (reduction to diselenide 6) and dialkylamines (formation of selenenamide 11).Decomposition of 15 in the presence of dibenzylamine resulted in trapping of a selenenic acid-like species (RSeSeOH) to give RSeSeN(CH2Ph)2 (R=PhC(O)C(CH3)2).Although 15 could not be prepared by oxidation of diselenide 6, it was possible to prepare a cyclic selenolseleninate (4,4-dimethyl-1,2-diselenolane monooxide, 20) by oxidation of the related diselenide (19).Attempts to prepare more stable aliphatic selenenic acids by blocking the principal decomposition pathway of 15 were not successful.Thus 1-benzoyl-1-cyclopropaneselenenic acid was generated from 35-ox and 38-ox and 1-benzoyl-2,2-dimethylcyclopropaneselenenic from 39-ox.The former underwent normal disproportionation (to 36 and 37) even when prepared at -49 deg C.The latter gave what appeared to be a selenolseleninate (40) which again disproportionated at -17 deg C.
- Reich, Hans J.,Hoeger, Carl A.,Willis, W. W., Jr.
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p. 4771 - 4780
(2007/10/02)
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- Reactions of Trialkylsilyl Trifluoromethanesulfonates, I. - Synthesis of Trialkylsilyl Enol Ethers
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The reactions of the ketones 2,2-bromoketones 6, α,β-unsaturated ketones 8, 1,2-diketones, and aliphatic aldehydes 20 with trialkylsilyl triflates 1 in the presence of triethylamine (4) at room temperature yield the silyl enol ethers 3, 7, 9, 11, and 21.The silylation of the unsymmetrical ketones 12 with 1a/4 runs regioselectively in the thermodynamical sense using 1a/12 in excess and yields the enol ethers 13t.The course of this reaction is discussed briefly.
- Emde, Herbert,Goetz, Andreas,Hofmann, Karin,Simchen, Gerhard
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p. 1643 - 1657
(2007/10/02)
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