13513-82-1Relevant academic research and scientific papers
Transfer hydrogenation of ketones catalyzed by 1-alkylbenzimidazole ruthenium(II) complexes
Oezdemir, Ismail,Sahin, Neslihan,Cetinkaya, Bekir
, p. 205 - 209 (2007)
Six [RuCl2(1-alkylbenzimidazole)(p-cymene)] complexes have been prepared and the new compounds characterized by C, H, N analyses, 1H NMR, and 13C NMR. The reduction of ketones to alcohols via transfer hydrogenation was ach
Enantioselective metal-free reduction of ketones by a user-friendly silane with a reusable chiral additive
Varjosaari, Sami E.,Skrypai, Vladislav,Herlugson, Sharon M.,Gilbert, Thomas M.,Adler, Marc J.
, p. 2839 - 2843 (2018)
1-Hydrosilatrane, a safe and easy-to-handle reducing reagent that can be inexpensively accessed, has been shown to reduce prochiral ketones asymmetrically in the presence of chiral 1,2-aminoalcohols with ees ranging from 8% to 86%. The best result was achieved using ephedrine as the source of chirality, which is readily commercially available. The additive can be recovered through extraction and reused without any erosion of enantioselectivity.
New dipyridylamine ruthenium complexes for transfer hydrogenation of aryl ketones in water
Romain, Charles,Gaillard, Sylvain,Elmkaddem, Mohammed K.,Toupet, Loic,Fischmeister, Cedric,Thomas, Christophe M.,Renaud, Jean-Luc
, p. 1992 - 1995 (2010)
A new family of cationic organometallic chloro compounds of the type [(arene)Ru(N,N)(Cl)]+ containing N,N-chelating dipyridylamine ligands has been synthesized and isolated as the chloride salts, which are water soluble and stable to hydrolysis. The resulting mononuclear ruthenium complexes catalyze the transfer hydrogenation of aryl ketones in aqueous solution to give the corresponding alcohols with good conversion and interesting recyclability.
Unexpectedly small ortho-oxygen substituent effects on stabilities of benzylic carbocations
Fujio,Keeffe,More O'Ferrall,O'Donoghue
, p. 9982 - 9992 (2004)
Equilibrium constants are reported for the ionization of benzylic alcohols to carbocations stabilized by cyclic or acyclic o-alkyl or o-oxygen substituents. The measurements were stimulated by the observation of small or inverse effects of replacement of an o-CH2 group by O or S in the cyclopentyl ring of indanol (kO/kCH2 = 1.2) or in the cyclohexyl ring of tetralol (kO/kCH2 = 0.6, k S/kCH2 = 0.3) on rates of carbocation formation. Values of pKR (KR = [ROH][H+]/[R+]) have been obtained by combining rate constants, kH, for the acid-catalyzed ionization of the alcohols with kH2O for attack of water on the carbocation measured by the azide clock method. For carbocations derived from the following alcohols, values of pKR are as indicated: 1-indanol, -11.7; 2,3-dihydro-3-hydroxybenzofuran (benzofuran hydrate), -9.3; 1-tetralol, -12.2; 4-chromanol, -12.0; 4-thiochromanol, -12.3; o-methyl-1-phenylethanol, -13.8; o-methoxy-1-phenylethanol, -11.7. The measurements show that, in contrast to its small kinetic effect, the equilibrium effect of replacing the o-CH 2 group by O in the cyclopentyl ring of indanol is 250-fold, whereas the effect of the same replacement in the cyclohexyl ring of tetralol is only 1.6. It is concluded (a) that the efficiency of conjugation of annular o-oxygen substituents to a benzylic carbocation center is sensitive to conformational restrictions arising from ring strain and (b) that, in the case of indanol, the kinetic effect of the same oxygen atom is subject to an imbalance of favorable resonance and unfavorable inductive effects at the transition state.
Ruthenium complexes of triazole-based scorpionate ligands transfer hydrogen to substrates under base-free conditions
Kumar, Mukesh,Depasquale, Joseph,White, Nicholas J.,Zeller, Matthias,Papish, Elizabeth T.
, p. 2135 - 2144 (2013)
The first ruthenium complexes of bulky tris(triazolyl)borate (Ttz) ligands were synthesized, fully characterized, and studied as transfer hydrogenation catalysts. The structures of the complexes were (η6-arene)RuCl(N, N), where in each case N,N is a κ2-Ttz or bis(triazolyl)borate (Btz) ligand (arene = p-cymene (1, 3, 5, 6), benzene (2), C6Me 6 (4); N,N = TtzPh,Me* (1, 2), TtzMe,Me (3, 4), Ttz (5), Btz (6)). All but 5 were crystallographically characterized, and notably for 1 and 2 a rearranged ligand structure is observed (as indicated by an asterisk). These complexes were all effective catalysts for transfer hydrogenation of aryl ketones in isopropyl alcohol with base co-catalyst, with rates that were accelerated by moisture-free conditions. Complexes 1 and 2 are also effective catalysts for base-free transfer hydrogenation, and with 1 hydrogenation of several base-sensitive substrates was demonstrated. The ability of 1 to serve as a hydrogenation catalyst without base is attributed primarily to steric bulk, and a preliminary mechanism for formation of that active catalyst is proposed.
Cinchona-Alkaloid-Derived NNP Ligand for Iridium-Catalyzed Asymmetric Hydrogenation of Ketones
Zhang, Lin,Zhang, Ling,Chen, Qian,Li, Linlin,Jiang, Jian,Sun, Hao,Zhao, Chong,Yang, Yuanyong,Li, Chun
supporting information, p. 415 - 419 (2022/01/12)
Most ligands applied for asymmetric hydrogenation are synthesized via multistep reactions with expensive chemical reagents. Herein, a series of novel and easily accessed cinchona-alkaloid-based NNP ligands have been developed in two steps. By combining [Ir(COD)Cl]2, 39 ketones including aromatic, heteroaryl, and alkyl ketones have been hydrogenated, all affording valuable chiral alcohols with 96.0-99.9% ee. A plausible reaction mechanism was discussed by NMR, HRMS, and DFT, and an activating model involving trihydride was verified.
Pincerlike molybdenum complex and preparation method thereof, catalytic composition and application thereof, and alcohol preparation method
-
Paragraph 0125-0130, (2021/08/11)
The invention discloses a clamp-type molybdenum complex, a preparation method, a corresponding catalyst composition and application. The method comprises the steps: obtaining 9 molybdenum complexes with different structures through coordination reaction of 2-(substituent ethyl)-(5, 6, 7, 8-tetrahydroquinolyl) amine and a corresponding carbonyl molybdenum metal precursor; and catalyzing a ketone compound transfer hydrogenation reaction through a molybdenum complex to generate 40 alcohol compounds. The preparation method of the molybdenum complex is simple, high in yield and good in stability. For a transfer hydrogenation reaction of ketone, the molybdenum-based catalytic system has high catalytic activity and small molybdenum loading capacity, is used for production of aromatic and aliphatic alcohols, and has the advantages of simple method, small environmental pollution and high yield.
Visible-Light-Driven Catalytic Deracemization of Secondary Alcohols
Hu, Xile,Zhang, Zhikun
supporting information, p. 22833 - 22838 (2021/09/09)
Deracemization of racemic chiral compounds is an attractive approach in asymmetric synthesis, but its development has been hindered by energetic and kinetic challenges. Here we describe a catalytic deracemization method for secondary benzylic alcohols which are important synthetic intermediates and end products for many industries. Driven by visible light only, this method is based on sequential photochemical dehydrogenation followed by enantioselective thermal hydrogenation. The combination of a heterogeneous dehydrogenation photocatalyst and a chiral molecular hydrogenation catalyst is essential to ensure two distinct pathways for the forward and reverse reactions. These reactions convert a large number of racemic aryl alkyl alcohols into their enantiomerically enriched forms in good yields and enantioselectivities.
Mn(i) phosphine-amino-phosphinites: a highly modular class of pincer complexes for enantioselective transfer hydrogenation of aryl-alkyl ketones
Jayaprakash, Harikrishnan
supporting information, p. 14115 - 14119 (2021/10/25)
A series of Mn(i) catalysts with readily accessible and more π-accepting phosphine-amino-phosphinite (P′(O)N(H)P) pincer ligands have been explored for the asymmetric transfer hydrogenation of aryl-alkyl ketones which led to good to high enantioselectivities (up to 98%) compared to other reported Mn-based catalysts for such reactions. The easy tunability of the chiral backbone and the phosphine moieties makes P′(O)N(H)P an alternative ligand framework to the well-known PNP-type pincers.
Arene-Immobilized Ru(II)/TsDPEN Complexes: Synthesis and Applications to the Asymmetric Transfer Hydrogenation of Ketones
Doherty, Simon,Knight, Julian G.,Alshaikh, Hind,Wilson, James,Waddell, Paul G.,Wills, Corinne,Dixon, Casey M.
supporting information, p. 226 - 235 (2020/12/31)
The Noyori-Ikariya (arene)Ru(II)/TsDPEN precatalyst has been anchored to amorphous silica and DAVISIL through the η6-coordinated arene ligand via a straightforward synthesis and the derived systems, (arene)Ru(II)/TsDPEN@silica and (arene)Ru(II)/TsDPEN@DAVISIL, form highly efficient catalysts for the asymmetric transfer hydrogenation of a range of electron-rich and electron-poor aromatic ketones, giving good conversion and excellent ee's under mild reaction conditions. Moreover, catalyst generated in situ immediately prior to addition of substrate and hydrogen donor, by reaction of silica-supported [(arene)RuCl2]2 with (S,S)-TsDPEN, was as efficient as that generated from its preformed counterpart [(arene)Ru{(S,S)-TsDPEN}Cl]@silica. Gratifyingly, the initial TOFs (up to 1085 h?1) and ee's (96–97 %) obtained with these catalysts either rivalled or outperformed those previously reported for catalysts supported by either silica or polymer immobilized through one of the nitrogen atoms of TsDPEN. While the high ee's were also maintained during recycle studies, the conversion dropped steadily over the first three runs due to gradual leaching of the ruthenium.
