In(OTf)₃‐Catalyzed Diastereoselective [2+3+1] Annulation of 3‐Formylchromones with α‐Methylstyrenes for Divergent Synthesis of Tetrahydroxanthones

An In(III)‐catalyzed [2+3+1] annulation strategy is developed for the diastereoselective construction of diversely functionalized tetrahydroxanthones bearing chromone rings. This protocol is based on a three‐component reaction involving various 3‐formylchromones and α ‐methylstyrenes via a carbonyl‐ene and formal [4+2] cycloaddition reaction. Notable features of this reaction include its wide substrate scope, high tolerance towards functional groups, atom economy, and excellent diastereoselectivity. In addition, the synthesized tetrahydroxanthones are readily transformed into 2‐hydroxybenzophenone products.