Stereospecific Intramolecular Reductive Cross-Electrophile Coupling Reactions for Cyclopropane Synthesis

The stereo­specific reductive
cross-electro­phile coupling
reaction of 2-aryl-4-chloro­tetra­hydro­pyrans to afford
disubstituted cyclo­propanes is reported. This ring contraction
presents surprises with respect to the stereo­chemical outcome
of reaction of the alkyl halide moiety. While cross-coupling and reductive
cross-electro­phile coupling reactions of alkyl halides are typically
stereo­ablative, using a chiral catalyst to set the stereo­center,
this transformation proceeds with high stereo­chemical fidelity
at the alkyl halide and ether bearing stereo­genic centers. This
approach provides straightforward access to highly substituted cyclopropanes
in two steps from commercially available aldehydes.