Pd-Catalyzed Allylic Alkylation Cascade with Dihydropyrans: Regioselective Synthesis of Furo[3,2‑<i>c</i>]pyrans

A regioselective palladium-catalyzed allylic alkylation cascade forms furo[3,2-<i>c</i>]pyrans from various cyclic β-dicarbonyl bis-nucleophiles and 3,6-dihydro-2<i>H</i>-pyran bis-electrophiles. The combination of allylic carbonate and anomeric siloxy leaving groups in the dihydropyran substrate allows control of the many regiochemical possibilities in this reaction. Annulation proceeds stereoconvergently to give <i>cis</i>-fused furopyrans from either <i>cis</i>- or <i>trans</i>-substituted starting material