Abstract:The first catalytic asymmetric PictetSpengler reaction of isatins is presented. BINOLderived phosphoric acids were found to be competent catalysts for this transformation, giving challenging spirooxindole structures bearing a quaternary stereocentre with generally good results. The 1,2,3,4-tetrahydro-b-carboline products (spiroindol-

Arylacetonitriles are able to participate in organocatalytic Michael additions to alpha,beta-unsaturated aldehydes by incorporating a nitro group at the phenyl ring, which acts as a temporary activating group in a remote position and allows further transformations. The sequential protocol Michael addition/NaBH(4) reduction/lactonization allows the synthesis of diastereomerically pure disubstituted lactones in high yield and optical purity.

A catalytic asymmetric addition of nitroalkanes to alkylideneindolenines, generated in situ from arylsulfonylindoles, is presented. Despite the weakness of the non-covalent H-bond interactions between catalyst and substrates, the performance of the bifunctional organocatalyst used was found to be essentially unaffected by the polarity of the reaction medium. Nitroalkanes, mostly used in nearly stoichiometric amounts, could thus function both as sol-vents and reagents, resulting in a truly solvent-free reaction. The broad substrate scope shown by the present transformation allowed the preparation of some optically active tryptamine precursors that are not accessible through the previous catalytic asymmetric methods.