Intramolecular Michael-type additions to vinyl bissulfoxides: Enantioselective synthesis of chiral aldehydes

The diastereoselective auxiliary-based intramolecular Michael-type additions to alkylidene bissulfoxides derived from dithiane and dithiolane were investigated. Utilization of substrates bearing N- and O-nucleophilic functions led to the formation of the respective cyclic substrates with selectivities ranging from 51:49 to 85:15. Cleavage of the bissulfoxide moiety by a two-step sequence yielded chiral carbaldehydes. The enantiomerically pure compounds obtained by this procedure, for example, tetrahydropyran-2-carbaldehyde and homopipecolic aldehyde, are hardly accessible by other routes. Both enantiomers of the target molecules are available since the stereochemical information is introduced with the readily available diethyl D- and L-tartrates.