130798-48-0Relevant academic research and scientific papers
London Dispersion Interactions Rather than Steric Hindrance Determine the Enantioselectivity of the Corey–Bakshi–Shibata Reduction
Eschmann, Christian,Song, Lijuan,Schreiner, Peter R.
supporting information, p. 4823 - 4832 (2021/02/01)
The well-known Corey–Bakshi–Shibata (CBS) reduction is a powerful method for the asymmetric synthesis of alcohols from prochiral ketones, often featuring high yields and excellent selectivities. While steric repulsion has been regarded as the key director of the observed high enantioselectivity for many years, we show that London dispersion (LD) interactions are at least as important for enantiodiscrimination. We exemplify this through a combination of detailed computational and experimental studies for a series of modified CBS catalysts equipped with dispersion energy donors (DEDs) in the catalysts and the substrates. Our results demonstrate that attractive LD interactions between the catalyst and the substrate, rather than steric repulsion, determine the selectivity. As a key outcome of our study, we were able to improve the catalyst design for some challenging CBS reductions.
Towards a General Understanding of Carbonyl-Stabilised Ammonium Ylide-Mediated Epoxidation Reactions
Novacek, Johanna,Roiser, Lukas,Zielke, Katharina,Robiette, Rapha?l,Waser, Mario
, p. 11422 - 11428 (2016/08/03)
The key factors for carbonyl-stabilised ammonium ylide-mediated epoxidation reactions were systematically investigated by experimental and computational means and the hereby obtained energy profiles provide explanations for the observed experimental results. In addition, we were able to identify the first tertiary amine-based chiral auxiliary that allows for high enantioselectivities and high yields for such epoxidation reactions.
Organocatalytic enantioselective α-hydroxymethylation of aldehydes: Mechanistic aspects and optimization
Boeckman, Robert K.,Biegasiewicz, Kyle F.,Tusch, Douglas J.,Miller, John R.
, p. 4030 - 4045 (2015/05/05)
Further studies of the direct enantioselective α-hydroxymethylation of aldehydes employing the α,α-diarylprolinol trimethylsilyl ether class of organocatalysts are described. This process has proven efficient for access to β-hydroxycarboxylic acids and δ-hydroxy-α,β-unsaturated esters from aldehydes in generally good yields, excellent enantioselectivity, and compatibility with a broad range of functional groups in the aldehyde. The goal of these studies was to identify the critical reaction variables that influence the yield and enantioselectivity of the α-hydroxymethylation process such as catalyst structure, pH of the medium, purity of the reactants and reagents particularly with respect to the presence of acidic impurities, and the nature of the buffer, along with the standard variables including solvent, time, temperature and mixing efficiency. The previously identified intermediate lactol has been further characterized and its reactivity examined. These studies have led to identification of the most critical variables translating directly into improved substrate scope, reproducibility, enantioselectivity, and yields.
Fluorinated organocatalysts for the enantioselective epoxidation of enals: Molecular preorganisation by the fluorine-iminium ion Gauche effect
Tanzer, Eva-Maria,Zimmer, Lucie E.,Schweizer, W. Bernd,Gilmour, Ryan
supporting information, p. 11334 - 11342,9 (2020/08/31)
The fluorine-iminium ion gauche effect is triggered upon union of a secondary β-fluoroamine and an α,β-unsaturated aldehyde, providing a useful strategy for controlling the molecular topology of intermediates that are central to organocatalytic processes. The β-fluoroamine (S)-2-(fluorodiphenylmethyl)pyrrolidine (1) is an effective catalyst for the enantioselective epoxidation of α,β-unsaturated aldehydes. A process of structural editing has revealed that the efficiency of this catalyst is due to the (fluorodiphenyl)methyl group when it is embedded in a β-fluoroiminium motif. Epoxidations of challenging cyclic α,β-disubstituted, β,β-disubstituted and α,β,β-trisubstituted enals catalysed by 1 proceed with excellent levels of enantiocontrol (up to 98 % ee). Fluorine finesse. The β-fluoroamine (S)-2-(fluorodiphenylmethyl)pyrrolidine (1) is an effective catalyst for the enantioselective epoxidation of α,β-unsaturated aldehydes (see scheme). Application of this catalyst to challenging cyclic α,β-disubstituted enals, β,β-disubstituted enals, and an α,β,β-trisubstituted enal proceeds in a highly enantioselective fashion (up to 98 % ee). Copyright
Asymmetric reduction of ketimines with trichlorosilane employing an imidazole derived organocatalyst
Gautier, Franois-Moana,Jones, Simon,Martin, Stephen J.
supporting information; experimental part, p. 229 - 231 (2009/03/11)
Organocatalysts for the asymmetric reduction of ketimines are presented that function well at low catalyst loadings providing chiral amines in good yield and enantioselectivity, the latter appearing to be independent of the ketimine substrate geometry.
Chiral compounds and their use as doping agents in liquid crystals
-
, (2008/06/13)
Chiral prolinol derivatives of formula (1). The compounds may be used as doping agents for liquid crystals for a wide range of applications, including solid state cholesteric filters for projection displays, circular polarizers and optical filters.
A Practical Enantioselective Synthesis of α,α-Diaryl-2-pyrrolidinemethanol. Preparation and Chemistry of the Corresponding Oxazaborolidines
Mathre, David J.,Jones, Todd K.,Xavier, Lyndon C.,Blacklock, Thomas J.,Reamer, Robert A.,et al.
, p. 751 - 762 (2007/10/02)
A practical two-step enantioselective synthesis of α,α-diaryl-2-pyrrolidinemethanols (1) from proline, based on the addition of aryl Grignard reagents to proline-N-carboxanhydride (3), is reported.An investigation into the chemistry of the corresponding B-alkyl- and B-aryloxazaborolidines (2) led to the development of a reliable procedure for their preparation.
A NEW CHIRAL CATALYST FOR THE ENANTIOSELECTIVE SYNTHESIS OF SECONDARY ALCOHOLS AND DEUTERATED PRIMARY ALCOHOLS BY CARBONYL REDUCTION
Corey, E. J.,Link, John O.
, p. 6275 - 6278 (2007/10/02)
An efficient synthesis of (S)-(-)-2-(di-β-naphthylhydroxymethyl)pyrrolidine (1) makes available the oxazaborolidine derivates 2 and 3 which are excellent catalysts for borane reduction of a variety of achiral ketones to chiral secondary alcohols, e.g. acetophenone, 98percent ee; α-tetralone, 95percent ee; and methyl-4-oxo-4-phenyl butyrate, 96percent ee.The synthesis of chiral 1-deuterio primary alcohols from achiral aldehydes with B-n-butyloxazaborolidine (4) as catalyst in the presence of 2H-catecholborane as reductant has also been demonstrated, e.g. benzaldehyde, 95percent ee; cyclohexanecarboxaldehyde, 92percent ee; and n-octanal, 90percent ee.
