Organocatalytic asymmetric spirocyclization reactions of cyclic 2,4-dienones with cyanoketones: synthesis of spiro-dihydropyrano cyclohexanones.

The first organocatalytic asymmetric synthesis of spiro-dihydropyrano cyclohexanones has been developed via the cascade reaction between cyanoketones and cyclic 2,4-dienones. A cinchona alkaloid-derived bifunctional primary amine catalyst in combination with N-Boc-tleucine was found to be the most effective for this spirocyclization reaction and provided the desired products in moderate to good yields with high enantioselectivities.

Organocatalytic asymmetric synthesis of dihydrofuran-spirooxindoles from benzylidene malononitriles and dioxindoles.

The first organocatalytic enantioselective synthesis of dihydrofuran-spirooxindoles having a linkage at the 2-position of the dihydrofuran motif has been developed. Dioxindoles and benzylidene malononitriles were employed in this method. The desired spirooxindole products were obtained via a Michael reaction followed by a Pinner reaction and isomerization and good to high yields with moderate diastereo and good to high enantioselectivities were observed.

Organocatalytic Asymmetric Synthesis of Bridged Acetals with Spirooxindole Skeleton.

The first highly diastereo- and enantioselective synthesis of bridged O, O-acetals embedded with spirooxindoles has been developed. Dioxindoles and 2-hydroxy cinnamaldehydes were employed as the reaction partners in this method. The desired products were obtained via diaryl prolinol TBS ether catalyzed Michael reaction followed by acetal formation with TFA.

Organocatalytic Asymmetric Michael-Hemiacetalization Reaction Between 2-Hydroxyacetophenones and Enals: A Route to Chiral β,γ-Disubstituted γ-Butyrolactones.

The first highly enantioselective organocatalytic reaction employing 2-hydroxyacetophenones is disclosed, namely Michael-hemiacetalization reaction of 2-hydroxyacetophenones with enals. The combination of a primary amine and a secondary amine catalyst was found to be the best choice for this methodology. The products of this reaction were obtained in high enantio- and diastereoselectivities and were converted to a variety of biologically important γ-butyrolactones.