4061-29-4Relevant academic research and scientific papers
Flexible stereoselective functionalizations of ketones through umpolung with hypervalent iodine reagents
Mizar, Pushpak,Wirth, Thomas
supporting information, p. 5993 - 5997 (2014/06/10)
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).
Enantioselective reduction of α-substituted ketones mediated by the boronate ester TarB-NO2
Eagon, Scott,Ball-Jones, Nicholas,Haddenham, Dustin,Saavedra, Jaime,Delieto, Cassandra,Buckman, Matthew,Singaram, Bakthan
supporting information; experimental part, p. 6418 - 6421 (2010/12/30)
A facile and mild reduction procedure is reported for the preparation of chiral secondary alcohols prepared from α-substituted ketones using sodium borohydride and the chiral boronate ester (l)-TarB-NO2. Direct reduction of substituted ketones bearing Lewis basic heteroatoms generally provided secondary alcohols of only modest enantiomeric excess likely due to either competition between the target carbonyl and the functionalized sidechains at the Lewis acidic boron atom in TarB-NO2 or the added steric bulk of the α-sidechain. As an alternative method, these substrates were synthesized using TarB-NO2 via a two-step procedure involving the reduction of an α-halo ketone to a chiral terminal epoxide, followed by regioselective/regiospecific epoxide opening by various nucleophiles. This procedure provides access to a variety of functionalized secondary alcohols including β-hydroxy ethers, thioethers, nitriles, and amines with enantiomeric excesses of 94% and yields up to 98%.
Asymmetric synthesis of β-dialkylamino alcohols by transfer hydrogenation of α-dialkylamino ketones
Kosmalski, Tomasz,Wojtczak, Andrzej,Zaidlewicz, Marek
experimental part, p. 1138 - 1143 (2009/09/27)
Transfer hydrogenation of representative aryl and heteroaryl dialkylaminomethyl ketones with formic acid-triethylamine, catalyzed by RuCl[(R,R)-TsDPEN](η-p-cymene), produces the corresponding β-dialkylamino alcohols, 97-99% ee, in 50-73% yields. Asymmetric synthesis of (R)-macromerine, 98% ee, the cactus Coryphantha macromeris alkaloid, is also described.
Substituent Effects on the Strength of C-C Bonds, 14. - Kinetic and Thermodynamic Stability of 2,3-Bis(dialkylamino)-1,4-diketones - Energy of Stabilization of α-Dialkylamino α-Carbonylalkyl Radicals with Capto-dative Substituents
Welle, Frank,Verevkin, Sergej P.,Keller, Manfred,Beckhaus, Hans-Dieter,Ruechardt, Christoph
, p. 697 - 710 (2007/10/02)
The equilibrium constants and rate constants for the dissociation of the 2,3-bis(dialkylamino)-1,4-diketone diastereomers meso- and DL-7a and 7b were measured over a temperature range of 40 deg C.From the enthalpies of dissociation ΔHDiss and ethalpies of activation ΔH(excit.) and the strain enthalpies of 7 the bond dissociation enthalpies BDE(C-C) of 7 were determined.By comparison with the dissociation enthalpies of Ct-Ct alkanes the change of these BDEs(C-C) by the capto-dative substitution was determined to be 85.4 kJ mol-1 (20.4 kcal mol-1).The heats of formation ΔHf0(g) of a series of amino ketones 8 were determined from their heats of combustion and their heats of evaporation.From the ΔHf0(g) values in combination with MM2 calculations of their strain enthalpies strain-free increments CHn2-n> with n = 0, 1, 2 were derived and geminal interaction enthalpies in the ground states were obtained thereof.The radical stabilization enthalpy RSE of 6 was deduced from the ΔBDE(C-C) values and the ground state effect to be 73.6 kJ mol-1 (17.6 kcal mol-1).From these data and the radical stabilization enthalpies RSE of α-aminoalkyl radicals (4.2 kJ mol-1) and α-carbonyl radicals (28.9 kJ mol-1) a synergetic radical stabilization enthalpy of 40.5 kJ mol-1 (9.7 kcal mol-1) is deduced.This number combines "extra" resonance stabilization and general inductive or anomeric geminal substituent interaction in the radicals.The crystal structure of meso-7a has been determined by X-ray diffraction methods. - Key Words: C-C Bond cleavage, kinetics of / Heats of formation / Radicals, stability of / Capto-dative effect / Geminal substituents, energetic interaction of
Boranes in Synthesis. 2. Asymmetric Synthesis of β-Amino Alcohols. A Facile Conversion of 2-Amino Acetophenones to the Corresponding β-Amino Alcohols in High Enantiomeric Purity
Beardsley, David A.,Fisher, Gary B.,Goralski, Christian T.,Nicholson, Lawrence W.,Singaram, Bakthan
, p. 1511 - 1514 (2007/10/02)
The asymmetric reduction of 2-amino acetophenones with Ipc2BH or Ipc2BCl at -78 deg C, yields the corresponding β-amino alcohols in good to excellent yields.Although only modest (12-45percent ee) enantiomeric excesses were obtained with Ipc2BH, 75-99perce
Chiral phosphinopyrrolidine compounds and their use for asymmetric synthesis of optically active compounds
-
, (2008/06/13)
New chiral phosphinopyrrolidine compounds of the general formula: STR1 wherein R1 is a hydrogen atom, --COR, --COOR, --CONHR or --SO2 --R where R is an alkyl or aryl group, R2 and R3 each represents independently an aryl group which may have a substituent or substituents, and R4 and R5 each represents independently an aliphatic or cycloaliphatic hydrocarbyl group which may have a substituent or substituents, as well as the use of these compounds as ligand for a metal complex catalyst for asymmetric synthesis of optically active compounds. The new chiral phosphinopyrrolidine compounds are useful ligands which attain both of high optical yield and high reaction efficiency in catalytic asymmetric reduction.
N,N-DIALKYLAMINOMETHYLTRIBUTYLTINS AS PRECURSORS OF (N,N-DIALKYLAMINOMETHYL) KETONES
Verlhac, Jean-Baptiste,Quintard, Jean-Paul
, p. 2361 - 2364 (2007/10/02)
(N,N-Dialkylaminomethyl) ketones have been obtained in good yields (64-87percent) by reacting (N,N-dialkylaminomethyl) tributyltins with acyl chlorides.The mildness of the experimental conditions is compatible with the presence of functional groups like a
