Enantioselective trapping of palladium-stabilized oxo-1,4-dipoles with photochemically generated ketenes

An enantioselective [4+2] cycloadditions of 2-alkylidenetrimethylene carbonates with photochemically generated ketenes was first accomplished by utilizing readily available chiral palladium catalysts. This unique protocol provided a variety of chiral lactones bearing a chiral all-carbon quaternary stereocenter in generally high reaction efficiency and selectivity under mild conditions.