Asymmetric Synthesis of cis-3,4-Disubstituted Chromans and Dihydrocoumarins via an Organocatalytic Michael Addition/ Hemiacetalization Reaction

The organocatalytic domino Michael/hemiacetalization reaction between various aldehydes and ortho‐nitrovinylphenols has been developed. Under the catalysis of diphenyl prolinol trimethylsilyl ether, cis‐3,4‐disubstituted chromanols are obtained in high to excellent yields (81–98%) and stereoselectivities (dr: 86:14 to >99:1, ee 96 to >99%). The corresponding disubstituted chromans are available by dehydroxylation of the domino products in good to excellent yields (58–95%). Furthermore, oxidation of the domino products with pyridinium chlorochromate provided 3,4‐dihydrocoumarins in good yields (65–83%) without any epimerization.