Synthesis of Functionalized Chromenes and Benzofurans from Aryloxy Propargyl Malonates

Abstract : A series of aryloxy propargyl malonates was efficiently converted into various chromenes by a gold-catalyzed cyclization/Brønsted acid catalyzed isomerization sequence, and the chromenes were subsequently converted into benzofurans by implementing an additional photochemical rearrangement. The photochemically induced ring contraction was proven to involve the intermediate formation of dienones.