Racemic and Stereoselective Phospha ‐Michael Addition of Chromones and Further Oxidation of C2‐Phosphorylated Chromanones

We herein report a Zn(OTf) 2 ‐catalyzed highly efficient phospha ‐Michael addition of P(O)─H compounds to substituted chromones, which provides a general protocol for the preparation of C2‐phosphorylated chromanones. Compared to previous reports, the current method benefits from the use of only 10 mol% of inexpensive catalyst Zn(OTf) 2 , relatively lower temperature, and a much wider substrate scope, especially regarding P(O)‐H compounds (aryl and alkyl H ‐phosphine oxides, H ‐phosphonates, and H ‐phosphinates). The resulting adducts can further undergo dehydrogenative oxidation to afford C2‐phosphorylated chromones, which also serve as a good supplement to previous reports. Catalytic asymmetric investigation reveals the use of BINOL‐derived CPA could enable the formation of C2‐phosphorylated chromanones with a tertiary phosphorus‐substituted carbon center in up to 94% yield with 75% ee.