An efficient and enantioselective approach to 2,5-disubstituted dihydropyrones

A highly efficient method for the formation of optically active 2,5-disubstituted dihydropyrones using catalytic enantioselective hetero-Diels-Alder reaction of (E)-3-methyl-4-methoxy-2[(trimethylsilyl)oxy]-1,3-butadiene with aldehydes is presented. In the presence of 5 mol% chiral titanium(IV) complex, this catalytic reaction proceeded smoothly to afford corresponding dihydropyrones in moderate to excellent yields with high enantioselectivities (up to 99% ee).