Synthesis of Heterocyclic-Fused Benzopyrans via the Pd(II)-Catalyzed C—H Alkenylation/C—O Cyclization of Flavones and Coumarins.

Abstract: An efficient and practical method for effecting a tandem C-H alkenylation/C-O cyclization has been achieved via the C-H functionalization of flavone derivatives. The synthetic utility of the one-pot sequence was demonstrated by obtaining convenient access to coumarin-annelated benzopyrans. The reaction scope for the transformation was found to be fairly broad, affording good yields of a wide range of flavone- or coumarin-fused benzopyran motifs, which are privileged structures in many biologically active compounds.