Asymmetric organocatalytic multicomponent reactions for efficient construction of bicyclic compounds bearing bisacetal and isoxazolidine moieties.

An organocatalytic multicomponent reaction of N-protected hydroxylamines, acrylaldehyde and acetal-containing enones was developed. Bisacetal-containing bicyclic isoxazolidine derivatives bearing four continuous stereocenters were formed with excellent stereoselectivities. A plausible reaction pathway was proposed based on O-labeling control experiments.

Asymmetric Organocatalytic Sequential Reaction of Structurally Complex Cyclic Hemiacetals and Functionalized Nitro-olefins To Synthesize Diverse Heterocycles.

Structurally complex cyclic hemiacetals bearing a racemic tetrasubstituted stereocenter have been prepared in a concise manner and were successfully used in an organocatalytic enantioselective sequence to react with functionalized nitro-olefins, providing bicyclic acetal-containing compounds as two separable epimers with excellent stereoselectivity. The reaction showed broad substrate scope, with respect to the starting hemiacetals. Moreover, this protocol allows the synthetic transformation of the products to various interesting heterocyclic compounds with substantial structural diversity and broad functionality.