Enantioselective [4 + 1] cycloaddition of ortho-quinone methides and bromomalonates under phase-transfer catalysis.

An enantioselective [4 + 1] cycloaddition reaction of ortho-quinone methides and bromomalonates using a quinine and BINOL derived phase-transfer catalyst is described. With high yields and enantioselectivities, the method provided a variety of optically active dihydrobenzofurans, which represent a valuable structural motif present in numerous naturally occurring and biologically active molecules.