- Enantioselective, organocatalytic reduction of ketones using bifunctional thiourea-amine catalysts
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Prochiral ketones are reduced to enantioenriched, secondary alcohols using catecholborane and a family of air-stable, bifunctional thiourea-amine organocatalysts. Asymmetric induction is proposed to arise from the in situ complexation between the borane and chiral thiourea-amine organocatalyst resulting in a stereochemically biased boronate-amine complex. The hydride in the complex is endowed with enhanced nucleophilicity while the thiourea concomitantly embraces and activates the carbonyl.
- Li, De Run,He, Anyu,Falck
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supporting information; experimental part
p. 1756 - 1759
(2010/10/04)
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- Enantioselective catalytic addition of nitroesters to N-carboalkyloxy imines: a route to quaternary stereocenters
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A readily available, low cost bifunctional organic catalyst promoted the addition of nitroesters to imines; in the reaction between 2-nitropropionates and N-Boc protected aldehyde-imines the product bearing a new quaternary stereocenter was obtained in up
- Puglisi, Alessandra,Raimondi, Laura,Benaglia, Maurizio,Bonsignore, Martina,Rossi, Sergio
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supporting information; experimental part
p. 4340 - 4342
(2009/10/26)
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- Stereoselective nucleophilic addition to imines catalyzed by chiral bifunctional thiourea organocatalysts
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A new and easy synthesis of chiral bifunctional organic catalysts obtained by the combination of (S)-t-leucine-derivatives with (1R,2R)-trans-1,2-diamino-cyclohexane was developed. A few compounds, representatives of a class of organocatalysts containing a thiourea group and a tertiary amino group connected through a chiral backbone, have been successfully synthesized. The catalytic behaviour of such bifunctional chiral molecules, either neutral or protonated species, was investigated in the addition of acetylacetone to β-nitrostyrene as a model reaction. Using the best conditions, high yields and enantioselectivities of up to 85% were obtained. The same metal free catalysts were then employed in the addition of activated nucleophiles to imines: in the reaction of 1,3-diketones with N-CBz imines, the products were isolated in up to 61% ee, while in the reaction with diethyl malonate enantioselectivities up to 71% were reached.
- Puglisi, Alessandra,Benaglia, Maurizio,Annunziata, Rita,Rossi, Davide
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experimental part
p. 2258 - 2264
(2009/04/04)
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- Highly enantioselective aza-Baylis-Hillman reactions catalyzed by chiral thiourea derivatives
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We report the discovery of asymmetric aza-Baylis-Hillman (ABH) reactions of N-p-nitrobenzenesulfonylimines with methyl acrylate catalyzed by chiral thiourea derivatives. A series of aromatic imines was found to undergo coupling with methyl acrylate with u
- Raheem, Izzat T.,Jacobsen, Eric N.
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p. 1701 - 1708
(2007/10/03)
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- Asymmetric catalytic Mannich reactions catalyzed by urea derivatives: Enantioselective synthesis of β-aryl-β-amino acids
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Highly enantioselective addition reactions between silyl ketene acetals and N-Boc aldimines are catalyzed by the thiourea-based catalyst 1c. Extraordinary scope is observed in this methodology with regard to the imine substrate, with aryl and heteroaromatic derivatives generally affording nearly quantitative yields of β-amino ester product in up to 98% enantioselectivity. Copyright
- Wenzel, Anna G.,Jacobsen, Eric N.
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p. 12964 - 12965
(2007/10/03)
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