Enantioselective organocatalytic domino Michael-acetalization-Henry reactions of 2-hydroxynitrostyrene and aldehyde for the synthesis of tetrahydro-6H-benzo[c]chromenones

Asymmetric domino Michael-acetalization reactions of 2-hydroxynitrostyrene and aldehydes on water followed by oxidation providing the cis-3,4-disubstituted dihydro-coumarins with excellent enantioselectivities (up to >99% ee). The variant with glutaraldehyde underwent a highly stereoselective domino Michael-acetalization-Henry reaction to afford the tetrahydro-6H-benzo[c] chromen-6-ones after the subsequent oxidation.