Asymmetric Synthesis of Spiro-3,4-dihydropyrans via a Domino Organocatalytic Sequence

A cinchona alkaloid-catalyzed domino Michael/hemiacetalization reaction of cyclic beta-oxo aldehydes and aromatic beta,gamma-unsaturated alpha-keto esters, resulting in the formation of spiro-dihydropyran architectures in good yield with high stereoselectivity (up to 97% ee), is presented.