A new strategy in enantioselective intramolecular hetero Diels-alder reaction: catalytic double asymmetric induction during the tandem transetherificaton-intramolecular hetero Diels-alder reaction of methyl (E)-4-methoxy-2-oxo-3-butenoate with rac-6-

摘要

An efficient catalytic double asymmetric induction during the tandem transetherification-intramolecular hetero Diels-Alder reaction has been developed. The enantioselective tandem reaction of methyl (E)-4-methoxy-2-oxo-3-butenoate with rac-6-methyl-5-hepten-2-ol has been achieved to provide methyl (2R,4aS,8aR)-3,4,4a,8a-tetrahydro-2,5,5-trimethyl-2H,5H-pyrano[4,3-b]-pyran-7-carboxylate in good yield with effective kinetic resolution (up to 95% selectivity), high diastereoselectivity (up to 92% de), and high enantioselectivity (up to 97% ee) in the presence of (S,S)-tert-Bu-bis(oxazoline)-Cu(SbF_6)_2 and 5 A molecular sieves.