A new strategy in enantioselective intramolecular hetero Diels–Alder reaction: catalytic double asymmetric induction during the tandem transetherification–intramolecular hetero Diels–Alder reaction of methyl ( E)-4-methoxy-2-oxo-3-butenoate with rac-6-methyl-5-hepten-2-ol

Abstract

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 (2 R,4a S,8a R)-3,4,4a,8a-tetrahydro-2,5,5-trimethyl-2 H,5 H-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 Å molecular sieves.