Cascade Claisen Rearrangement: Rapid Synthesis of Polysubstituted Salicylaldehydes and Total Syntheses of Hemigossypol and Gossypol

Abstract A cascade Claisen rearrangement of a well‐organized maltol propargyl ether for the construction of polysubstituted salicylaldehydes is reported. This reaction features high atom economy (100 %), as well as catalyst‐free and gram‐scale conditions. Based on this novel methodology, the total synthesis of hemigossypol, gossypol, and their analogues has been realized.