Highly Enantio- and Diastereoselective [4 + 2] Cycloaddition of 5H-oxazol-4-ones with N-Maleimides

Highly diastereo- and enantioselective C2 addition of 5H-oxazol-4-ones to γ-keto-α,β-unsaturated esters

The direct C2-addition of 5H-oxazol-4-ones to γ-keto-α,β-unsaturated esters catalyzed by a chiral squaramide has been achieved. Diverse highly functionalized γ-keto esters bearing a C2-oxazolone at the α-position were afforded in high yields with excellent stereoselectivities (d.r. > 20 : 1 and up to 98% ee).

Organocatalytic Enantioselective Michael Reaction of Aminomaleimides with Nitroolefins Catalyzed by Takemoto's Catalyst

Known as electrophiles, maleimides are often used as acceptors in Michael additions to produce succinimides. However, reactions with maleimides as nucleophiles for enantioselective functionalization are only rarely performed. In this paper, a series of bifunctional Takemoto's catalysts were used to organocatalyze the enantioselective Michael reaction of aminomaleimides with nitroolefins. The resulting products were obtained in good yields (76-86%) with up to 94% enantiomer excess (ee). The catalyst type and the substrate scope were broadened using this methodology.

Non-hydrogen bond catalyst-mediated diastereoselective conjugate additions of 5H-oxazol-4-ones to o-hydroxyphenyl-substituted p-quinone methides

An efficient DBU-catalyzed conjugate addition of 5H-oxazol-4-ones to o-hydroxyphenyl-substituted p-quinone methides has been developed, affording the valuable diarylmethanes in high yields with excellent diastereoselectivity. This strategy demonstrates a robust access to a wide range of diarylmethane derivatives possessing biologically significant o-hydroxyphenol and p-hydroxyphenol moieties under mild reaction conditions.

Stereoconvergent 1,4-Addition Reaction of 5H-Oxazol-4-ones with E,Z Isomeric Mixture of Alkylidene β-Ketoesters Catalyzed by Chiral Guanidines

A 1,4-addition reaction of 5H-oxazol-4-ones to alkylidene β-ketoesters, which was catalyzed by using chiral guanidines via a dynamic kinetic resolution process that involved geometric isomerization of the alkylidene β-ketoesters, was developed. This method allowed using E,Z isomeric mixture of various acyclic alkylidene β-ketoesters to obtain the products stereoselectively. The relation between the geometry and the stereoselectivity of products was investigated, and the derivatization of the products to the corresponding α-acyl-γ-lactone was performed.

Organocatalytic asymmetric domino Michael/O-alkylation reaction for the construction of succinimide substituted 3(2H)-furanones catalyzed by quinine

Asymmetric domino reaction of maleimides with γ-halogenated-β-ketoesters catalyzed by quinine is developed to give succinimide substituted 3(2H)-furanones in good enantioselectivities.