Direct asymmetric aldol reaction of acetone with α-ketoesters catalyzed by primary–tertiary diamine organocatalysts

Recent advances in reactions promoted by amino acids and oligopeptides

During the last 20 years, Organocatalysis has become one of the major fields of Catalysis. Herein, we provide a recent overview on reactions where the use of amino acids and peptides as the organocatalysts was employed. All aspects regarding aldol reactions, Michael reactions, epoxidation, Henry reactions and many others that are crucial for the reaction conditions and reaction mechanisms are discussed.

Tripeptide-Catalyzed Asymmetric Aldol Reaction Between α-ketoesters and Acetone Under Acidic Cocatalyst-Free Conditions

Here, we report the tripeptide-catalyzed asymmetric aldol reaction between α-ketoesters and acetone under acidic cocatalysts-free conditions. H-Pro-Tle-Gly-OH 3g-catalyzed reactions between α-ketoesters and acetone resulted in up to 95% yield and 88% ee. Analysis of the transition state using density functional theory (DFT) calculations revealed that the tert-butyl group in 3g played an important role in enantioselectivity.

Primary-tertiary diamine-catalyzed Michael addition of ketones to isatylidenemalononitrile derivatives

Simple primary-tertiary diamines easily derived from natural primary amino acids were used to catalyze the Michael addition of ketones with isatylidenemalononitrile derivatives. Diamine 1a in combination with D-CSA as an additive provided Michael adducts in high yield (up to 94%) and excellent enantioselectivity (up to 99%). The catalyst 1a was successfully used to catalyze the three-component version of the reaction by a domino Knoevenagel–Michael sequence. The Michael adduct 4a was transformed into spirooxindole 6 by a reduction with sodium borohydride in a highly enantioselective manner.

Dynamic kinetic asymmetric transformations of β-stereogenic α-ketoesters by direct aldolization

Dynamic kinetic asymmetric transformations (DyKAT) of racemic β-bromo-α-keto esters by direct aldolization of nitromethane and acetone provide access to fully substituted α-glycolic acid derivatives bearing a β-stereocenter. The aldol adducts are obtained in excellent yield with high relative and absolute stereocontrol under mild reaction conditions. Mechanistic studies determined that the reactions proceed through a facile catalyst-mediated racemization of the β-bromo-α-keto esters under a DyKAT Type I manifold.

Asymmetric aldol reactions of α,β-unsaturated ketoester substrates catalyzed by chiral diamines

Highly efficient asymmetric aldol reactions between α,β-unsaturated keto esters and acyclic ketones catalyzed by chiral diamines are reported. The corresponding products were obtained in excellent yields with excellent enantioselectivities. The absolute configuration for the product was determined by X-ray analysis. A variety of substrates were tolerable in the present catalytic system.

Enantioselective Morita-Baylis-Hillman reaction of isatins with acrylates: facile creation of 3-hydroxy-2-oxindoles

The first tertiary amine catalyzed enantioselective Morita-Baylis-Hillman (MBH) reaction of isatins with acrylates has been demonstrated, allowing asymmetric synthesis of biologically significant 3-substituted-3-hydroxy-2-oxindoles in good yields and with excellent enantioselectivities. The C6'-OH group of β-isocupreidine (β-ICD) is believed to facilitate the key proton transfer step in the MBH reaction, via an intramolecular proton relay process.