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.