Stereoselective Synthesis of Dihydrocoumarins via [1,2]-Phospha-Brook Rearrangement in Three-Component Coupling Reaction of α-Ketoesters, -Quinone Methides, and Dialkyl Phosphites.

A highly regio- and diastereoselective approach for the synthesis of phosphate substituted dihydrocoumarins via Brønsted base catalyzed [1,2]-phospha-Brook rearrangement is reported. The two-step, one-pot Michael addition of α-phosphonyloxy enolates proceeds by coupling of dialkyl phosphite and α-ketoesters to -quinone methides, followed by an intramolecular cyclization, providing 3,4-dihydrocoumarin frameworks.