Solvent-Mediated Enantioselective Rauhut–Currier Cyclization via Iminium and Enamine Activation

In
this work, we have developed an unconventional and highly enantioselective
solvent-promoted Rauhut–Currier cyclization of enal-tethered
cyclohexadienone by exploiting the reactivity of a simple Jørgensen–Hayashi
catalyst through the merging of iminium and enamine activation. This
asymmetric desymmetrization reaction has broad substrate scope in
good yields with high to excellent enantioselectivity. DFT calculations
suggest that the elimination of the alkoxy group is the rate-limiting
step and that it proceeds through proton abstraction by solvent instead
of a direct 1,3-proton shift.