2008

ABSTRACT:

An efficient, organocatalytic enantioselective addition-cyclization reaction of cyclic 1,3-dicarbonyl compounds with different α,β-unsaturated aldehydes has been developed. The diarylprolinol ether-catalyzed reaction cascade provides a variety of chromenones, quinolinones and pyranones in good yields and with excellent enantioselectivities.

ABSTRACT:

A new asymmetric Brønsted acid-catalyzed cascade reaction involving a 1,4-addition, enantioselective protonation and 1,2-addition has been developed. This organocatalytic cascade not only provides for the first time 3- and 2,3-substituted tetrahydroquinolines and octahydroacridines in good yields with high dia- and enantioselectivities under mild reaction conditions but additionally represents the first example of a chiral Brønsted acid-catalyzed protonation reaction in an organocatalytic domino reaction. Furthermore, the new Brønsted acid-catalyzed hydride-proton-hydride transfer cascade can be applied to prepare new molecular scaffolds with up to three new stereocenters in an efficient one-pot reaction sequence.

ABSTRACT:

A direct asymmetric organocatalytic aza-Henry reaction has been developed in which a new bifuctional Brønsted-acid-catalyzed activation of nitroalkanes provides an efficient access to α,β-diamino acids with high dia- and enantioselectivities under mild and base-free reaction conditions.

ABSTRACT:

Depending on the catalyst (both N-triflylphosphoramides), the highly enantioselective Brønsted acid catalyzed addition of indoles to α,β-unsaturated carbonyl compounds provides either α-keto esters (up to 92 % ee, left side of the scheme), or a novel type of bisindole (right), which displays atropisomerism. The α-keto esters can also be converted into amino acids by a one-pot 1,4-addition-reductive amination reaction.

ABSTRACT:

An addition–cyclization reaction cascade triggered by an organocatalyst was used for the enantioselective preparation of a series of biologically active 1,2- and 1,4-pyranonaphthoquinones from aliphatic and aromatic α,β-unsaturated aldehydes and 2-hydroxy-1-4-naphthoquinone. A trimethylsilyl-protected diarylprolinol serves as the Lewis base organocatalyst.

ABSTRACT:

A highly enantioselective reaction has been developed for the three-component reaction of an enamine with a vinyl ketone and a Hantszsch ester in which each of the six reaction steps is catalyzed by the same chiral Brønsted acid (see scheme). This reaction offers efficient access to tetrahydropyridines and azadecalinones from simple and readily available starting materials.

ABSTRACT:

You can count on the counterion in ion-pair intermediates to induce high levels of asymmetry in the title reaction. The efficient transformation proceeds under mild reaction conditions in the presence of an air-stable N-triflylphosphoramide in a low catalyst loading of just 1 mol % to give substituted α-hydroxyesters in good yields and with excellent ee values (see scheme; R=aryl).

ABSTRACT:

A condensation–rearrangement sequence forms the basis of a high-yielding route to chiral homoallylic amines from readily accessible aldehydes (see scheme). This transformation is both the first enantioselective Brønsted acid catalyzed sigmatropic rearrangement and the first example of a catalytic asymmetric aza-Cope rearrangement.

ABSTRACT:

Valuable, biologically active chromenones such as those depicted were synthesized based on a diaryl prolinol ether catalyzed, enantioselective reaction of diketones with α,β-unsaturated aldehydes. In these efficient addition–acetalization cascade reactions, diverse aliphatic and aromatic α,β-unsaturated aldehydes, as well as various diketones, can be successfully applied and the 2-hydroxychromenones can be isolated in good yields and with excellent enantioselectivities.