A novel catalytic enantioselective tandem transetherification–intramolecular hetero Diels–Alder reaction of methyl (E)-4-methoxy-2-oxo-3-butenoate with δ,ε-unsaturated alcohols

A novel asymmetric tandem transetherification–intramolecular hetero Diels–Alder reaction of methyl (E)-4-methoxy-2-oxo-3-butenoate with δ,ε-unsaturated alcohols has been found to be catalyzed by optically active complexes based on bis(oxazoline) (box) chiral ligands and copper(II) cations. The catalyst derived from the (S,S)-tert-Bu-bis(oxazoline) and Cu(SbF6)2 in the presence of 5 Å molecular sieves was highly effective to afford corresponding trans-fused hydropyranopyran derivatives in good yield (up to 90%) with high enantiomeric excess (up to 98% ee).