Asymmetric Organocatalysis with Sulfones

Asymmetric organocatalysis has become a powerful tool for the synthesis of optically active compounds. Whereas early research mainly focused on combining simple reagents as a proof‐of‐concept for asymmetric organocatalysis, recent investigations are directed towards extending the concept to more target‐ and diversity‐oriented synthesis. As a result of the many transformation possibilities and their ability to generate both nucleophilic and electrophilic reaction partners, sulfones have become especially important substrates in the field of organocatalysis.     

Organocatalytic direct asymmetric alpha-heteroatom functionalization of aldehydes and ketones

The direct enantioselective introduction of a stereogenic carbon-heteroatom bond adjacent to a carbonyl functionality leads to optically active compounds of significant importance for e.g. the life-science industry. Organocatalytic enantioselective amination, oxygenation, fluorination, chlorination, bromination and sulfenylation of aldehydes and ketones, using chiral amines as the catalysts, are reviewed in this feature article. Furthermore, a few other transformations are also outlined. The scope, potential and application of these organocatalytic asymmetric reactions are presented and the mechanistic aspects discussed.     

Organocatalytic asymmetric allylic carbon-carbon bond formation

Organocatalytic allylic C-C bond-forming addition of activated alkylidenes to alkyl and aryl nitroalkenes has been achieved with high diastereo- and enantioselectivity. Chiral tertiary amine catalysts are used to give allyl intermediates which exhibit gamma-selectivity in the C-C bond forming step. The reactions proceed with up to >99:1 syn:anti ratio for both the alkyl- and aryl nitroalkenes with up 96% and 98% ee, respectively. The products of this conjugate addition are transformed into a range of intermediates, such as optically active conjugated dienes and 1-substituted tetralones, which are difficult to access via alternative methods.