- Zinc-Mediated Efficient and Selective Reduction of Carbonyl Compounds
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We herein describe for the first time that an optimized combination of Zn and NH4Cl can be used for the selective reduction of aldehydes and ketones to the corresponding alcohols. The aldehyde and keto groups are selectively reduced in the presence of azide, cyano, epoxy, ester, and carbon–carbon double-bond functional groups. A broad functional-group compatibility, chemoselective reduction of aldehydes in the presence of ketones, and selective reduction of isatins at the C3 carbonyl group are the highlights of the present method.
- Mandal, Tirtha,Jana, Snehasish,Dash, Jyotirmayee
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p. 4972 - 4983
(2017/09/13)
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- Pinacol couplings of a series of aldehydes and ketones with SmI2/Sm/Me3SiCl in DME
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The pinacol coupling is one of the most significant methods to synthesize vic-diols. The combination of samarium diiodide (SmI2) and samarium metal successfully induces the selective pinacol couplings of not only aromatic aldehydes and ketones but also aliphatic ones in the presence of trimethylchlorosilane (Me3SiCl) in 1,2-dimethoxyethane (DME). DME is the most suitable solvent for the reduction system using SmI2 and Me3SiCl. Me3SiCl, a widely available additive, prevents the decomposition of the formed vic-diols, i.e., meso-isomers, and controls their stereochemistry. In particular, the pinacol couplings of sterically hindered aliphatic aldehydes and ketones proceed with excellent diastereoselectivities to afford dl-isomers in good yields.
- Yoshimura, Aya,Saeki, Tomokazu,Nomoto, Akihiro,Ogawa, Akiya
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p. 5347 - 5355
(2015/07/15)
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- Electrochemical pinacol coupling of aromatic carbonyl compounds in a [BMIM][BF4]-H2O mixture
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The electrochemical pinacol coupling reactions of aromatic carbonyl compounds were carried out using an 80% [BMIM][BF4]-H2O mixture as the electrolytic medium. The corresponding diols were obtained in good to excellent yields with moderate diastereoselectivity. The stereoselectivity can be explained using the strongly-bound ion-pairs formed between the imidazolium cation and the radical anions of the carbonyl compounds. The ionic liquid replaces both organic solvents and supporting electrolytes generally used in the electrosynthetic method. The electrolytic medium can be recycled and successfully reused at least in five consecutive reactions.
- Kronenwetter, Hannah,Husek, Jakub,Etz, Brian,Jones, Aaron,Manchanayakage, Renuka
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supporting information
p. 1489 - 1495
(2014/03/21)
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- Study on improved diastereoselectivity in photo-induced electron transfer pinacol coupling reactions of substituted acetophenones
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Novel diastereoselective photo-induced pinacol coupling reactions of acetophenones by using triethylamine and chiral tertiary amines as electron donating co-sensitizers were studied. Various influence factors including solvents, substituents, and chiral a
- Ma, Nan,Shi, Wei,Zhang, Ronghua,Zhu, Zhiliang,Jiang, Zhiqin
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experimental part
p. 718 - 720
(2011/03/20)
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- Iron-catalyzed pinacol coupling of aryl ketones with a phenyltitanium reagent: A new type of catalytic reaction
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A reaction of aryl ketones with phenyltitanium triisopropoxide ([PhTi(Oi-Pr)3]) in the presence of [Fe(acac)3] as a catalyst (1 mol%) gave the corresponding pinacols in high yields. The catalytic cycle of this process involves an iron-catalyzed disproportionation of [PhTi(Oi-Pr) 3] into biphenyl and a lowvalent titanium species.
- Hayashi, Tamio,Sasaki, Keigo
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supporting information; experimental part
p. 492 - 494
(2011/06/25)
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- InCl3/Al mediated pinacol coupling reactions of aldehydes and?ketones in aqueous media
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A systematic work on the homo-pinacol coupling reactions of benzophenones, aldehydes, and acetophenones in aqueous media with InCl3/Al is described for the first time, in which various 1,2-diols are obtained in moderate to good yields.
- Wang, Chunyan,Pan, Yuanjiang,Wu, Anxin
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p. 429 - 434
(2007/10/03)
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- Indium-catalyzed reductive coupling of aromatic carbonyl compounds and imines in the presence of aluminum and chlorosilanes
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Reductive homocoupling of aromatic aldehydes, ketones, and imines has been achieved in tetrahydrofuran (THF) at room temperature using a catalytic amount of InCl3 (0.5-3.0 mol %) under a nitrogen atmosphere in the presence of chlorotrimethylsilane (TMSCl) and aluminum metal (Al) to provide the corresponding 1,2-diols and 1,2-diamines, respectively, in good to moderate yields. Other indium compounds such as In(NO3)3, cyclopentadienylindium, and indium metal have also been revealed to be effective as catalysts. The catalytic effect of the indium compound is remarkable, and, thus, without it, no reaction occurs in the case of aromatic aldehydes and aldimines, and an induction period is quite long in the case of aromatic ketones. Without either TMSCl or Al, no reaction proceeds even in the presence of the catalyst. Unfortunately, the diastereoselectivity of the products (dl and meso) is not high. Although the precise reaction scheme is not yet clear, we tentatively propose that a redox-active In-Al alloy might be formed on the surface of aluminum in the presence of TMSCl, and an electron transfer from the alloy to substrate might occur.
- Ohtaka, Seiji
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p. 309 - 316
(2007/10/03)
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- InCl3-catalyzed reductive coupling of aromatic carbonyl compounds in the presence of magnesium and chlorotrimethylsilane
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Reductive homocoupling of aromatic aldehydes and ketones has been achieved in tetrahydrofuran at room temperature using a catalytic amount of InCl3 (0.005-0.1 molar amount) under nitrogen atmosphere in the presence of both chlorotrimethylsilane and magnesium metal (Mg turnings) to provide the corresponding 1,2-diols in good to moderate yields with a high diastereoselectivity.
- Mori,Ohtaka,Uemura
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p. 1497 - 1498
(2007/10/03)
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- Pinacolization and reduction of aromatic carbonyls with aluminium-KOH
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A simple and rapid procedure for the pinacolization of aromatic aldehydes and reduction of hindered ketones with inexpensive aluminium and KOH in methanol at ambient temperature is reported. The pinacolization and reduction are proposed to be proceeding via single electron transfer from aluminium. Copyright 1996 by the Royal Society of Chemistry.
- Khurana, Jitender M.,Sehgal, Arti,Gogia, Amita,Manian, Aparna,Maikap, Golak C.
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p. 2213 - 2215
(2007/10/03)
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- STEREOSELECTIVE SYNTHESIS OF ERYTHRO- AND THREO-1,2-DIOLS FROM DIKETO SULFIDES VIA CIS-3,4-DIHYDROXYTHIOLANES
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Intramolecular reductive coupling reaction of a series of diketo sulfides (1) by a low-valent titanium reagent at 0 deg C in tetrahydrofuran leads to cis-3,4-dihydroxythiolanes (2) exclusively in 67-89percent yields.Desulfurization of 2 by Raney nickel in
- Nakayama, Juzo,Yamaoka, Shoji,Hoshino, Masamatsu
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p. 1799 - 1802
(2007/10/02)
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- Reduction of Aromatic Carbonyl Compounds Promoted by Titanium Trichloride in Basic Media. Stereochemistry Studies
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Aromatic ketones, which are not affected by Ti(III) chloride in acidic medium, react smoothly in basic media to afford the reductively coupled products according to the increase of the reducing power of Ti(III) ion with increasing pH.Benzil, benzoin, and methoxybenzoin give the corresponding alcohols.The observed stereochemistry is discussed in terms of intermolecular Ti bridging control (dl > meso) when intramolecular Ti complexation is prevented and in terms of steric control (meso > dl) when two sites of potential Ti complexation are available in the molecule.Thereagent, Ti(III) chloride, is selective in that many other functional groups are unaffected by it.
- Clerici, Angelo,Porta, Ombretta
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