- Zinc-Mediated Efficient and Selective Reduction of Carbonyl Compounds
-
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
-
p. 4972 - 4983
(2017/09/13)
-
- Synthesis of virtually enantiopure aminodiols with three adjacent stereogenic centers by epoxidation and ring-opening
-
A virtually complete enantioselective synthesis of 3-amino-1,2-diols with three consecutive stereocenters was accomplished by a sequential cascade of two kinetic resolutions, which features a Sharpless or Hafnium-catalyzed asymmetric epoxidation and a subsequent W-catalyzed aminolysis. Enantiopure products with up to >99.9% ee and >99.9:0.1 dr were obtained and could serve as potential building blocks for pharmaceutical or biological significant molecules.
- Luo, Lan,Yamamoto, Hisashi
-
supporting information
p. 10466 - 10470
(2015/11/10)
-
- Enantioselective one-pot catalytic synthesis of 4,5-epoxy-3-alkanols and 1-Phenyl-2,3-epoxy-1-alkanols from α,β-unsaturated aldehydes
-
Conformationally restricted perhydrobenzoxazines have been demonstrated to be good chiral ligands for one-pot asymmetric ethylation/epoxidation, and the unprecedented arylation/epoxidation of trisubstituted α,β-unsaturated aldehydes. The scope of the reaction has been studied and a wide set of substrates with allylic strain of different nature has been explored, obtaining good or total diastereoselectivities in all cases. The enantiocontrol was good or high for the ethylation/epoxidation reaction, whereas it remained at moderate or good levels for the arylation/epoxidation. The reaction is general for trisubstituted enals, and alkylic and aromatic substituents are tolerated at both the α- and β-position of the unsaturated aldehyde; however, disubstituted enals remain challenging substrates. When the one-pot and two-pot protocols were compared, no significant differences concerning the stereocontrol were found, so the advantages of the one-pot procedure are clear. Copyright
- Infante, Rebeca,Hernandez, Yulan,Nieto, Javier,Andres, Celia
-
supporting information
p. 4863 - 4869
(2013/08/23)
-
- Indium-promoted chemo- and diastereoselective allylation of α,β-epoxy ketones with potassium allyltrifluoroborate
-
A practical method for the chemo- and diastereoselective allylation of α,β-epoxy ketones has been developed by using the convenient air and moisture stable reagent potassium allyltrifluoroborate. Indium metal was found to promote addition in stoichiometric or catalytic amounts, to afford α,β-epoxyhomoallylic tertiary alcohols in high yields and diastereoselectivities, without competing ring-scission of the epoxide.
- Nowrouzi, Farhad,Janetzko, John,Batey, Robert A.
-
supporting information; experimental part
p. 5490 - 5493
(2011/02/27)
-
- Poly(per)fluoroalkanesulfonyl fluoride promoted olefin epoxidation with 30% aqueous hydrogen peroxide
-
Epoxidation of various electron rich olefins with a novel oxidation system of poly(per)fluoroalkanesulfonyl fluoride/hydrogen peroxide/base is reported.
- Yan, Zhaohua,Tian, Weisheng
-
p. 2211 - 2213
(2007/10/03)
-
- Asymmetric epoxidation via phase-transfer catalysis: Direct conversion of allylic alcohols into α,β-epoxyketones
-
Studies into the use of a chiral phase-transfer catalyst in conjunction with sodium hypochlorite to effect the enantio-selective formation of α,β-epoxyketones from allylic alcohols are described.
- Lygo, Barry,To, Daniel C. M.
-
p. 2360 - 2361
(2007/10/03)
-
- Applications of free and resin-bound novel (trifluoromethyl)dioxiranes
-
Recyclable resin-bound and other trifluoromethyl aryl ketones are efficient catalysts for oxone mediated epoxidations.
- Boehlow, Todd R.,Buxton, P. Christopher,Grocock, Estella L.,Marples, Brian A.,Waddington, Victoria L.
-
p. 1839 - 1842
(2007/10/03)
-
- Chemo- and stereoselective reduction of α,β-epoxyketones with diisopropoxytitanium(III) tetrahydroborate
-
Reduction of α,β-epoxyketones with diisopropoxytitanium(III) tetrahydroborate in dichloromethane under mild conditions (-78°→20°C) provides anti- (or erythro-) α,β-epoxy alcohols in high yields with high degree of chemo- and stereoselectivity.
- Ravikumar,Chandrasekaran, Srinivasan
-
p. 9137 - 9142
(2007/10/03)
-
- Novel Synthesis of syn-α,β-Epoxy Alcohols by Diastereoselective Carbonyl Reduction of α,β-Epoxy Ketones
-
A novel tin hydride reagent, Bu3SnH-Bu4NCN, reduced α,β-epoxy ketones to the corresponding syn-α,β-epoxy alcohols in high diastereoselectivities.
- Kawakami, Takayo,Shibata, Ikuya,Baba, Akio,Matsuda, Haruo,Sonoda, Noboru
-
p. 8625 - 8626
(2007/10/02)
-
- Oxiranyllithium reagents: Generation from organotin precursors, addition to aldehydes and ketones, and dimerization to α,α′-dialkoxyolefins
-
Oxiranyllithium compounds can be generated from organotin precursors by tin-lithium exchange with butyllithium in THF at -90°C. In the presence of TMEDA, they react with aldehydes and ketones to give epoxy alcohols in good yields. In the absence of TMEDA, they dimerize to α,α′-dialkoxyolefins.
- Lohse, Peter,Loner, Helena,Acklin, Pierre,Sternfeld, Francine,Pfaltz, Andreas
-
p. 615 - 618
(2007/10/02)
-
- A Novel Probe for Free Radicals featuring Epoxide Cleavage
-
This paper describes the identification of carbon-carbon bond cleavage within a defined range of epoxides as being a reaction type which is specifically diagnostic of free radicals adjacent to the epoxide.The speed of the epoxide cleavage is greater than
- Dickinson, Julia M.,Murphy, John A.,Patterson, Christopher W.,Wooster, Nicholas F.
-
p. 1179 - 1184
(2007/10/02)
-
- Solvent Microstructure Effect on Reaction Stereochemistry; Ring Opening of Chalcone Oxides
-
The stereochemistry and kinetics of acid-catalysed ring-opening reactions of epoxides are reported.Predominant inversion is found in the usual hydroxylic solvents.As the nucleophilicity of the solvent diminishes and acidity increases, the stereochemistry changes to predominant retention.Electron-donating substituents also tend to favour retention.In mixed solvents, the solvent microstructure is altered, leading to net retention for nucleophiles such as methanol.The exception is dioxane-methanol, which gives enhanced inversion.Molecular mechanics calculations indicate an electrostatic preference for the retention route, but a steric preference for inversion.The activation parameters indicate a negative entropy for both inversion and retention paths.Possible reasons are discussed for the entropy of the retention route being in the range normally found for A2 reactions.
- Durham, Dana,Kingsbury, Charles A.
-
p. 923 - 930
(2007/10/02)
-
- HIGHLY STEREOSELECTIVE SYNTHESIS OF OPTICALLY ACTIVE α,β-EPOXY ALCOHOLS
-
Stereoselective zinc borohydride reduction of optically active α,β-epoxy ketones affords the corresponding alcohols with enantiomeric excess up to 95percent.
- Banfi, S.,Colonna, S.,Molinari, H.,Julia, S.
-
p. 901 - 904
(2007/10/02)
-