Organocatalytic Asymmetric Cascade Michael-Acyl Transfer Reaction between 2-Fluoro-1,3-diketones and 2-Hydroxynitrostyrenes

An organocatalytic asymmetric cascade Michael-acyl transfer reaction of 2-hydroxynitrostyrenes and monofluorinated β-diketones has been developed employing a cooperative catalytic system. A combination of quinine-derived bifunctional squaramide catalyst and achiral hydrogen bond donor cocatalyst was found to be the most effective for this reaction and provided the fluorinated acyl transfer products in high yields with good diastereo- and excellent enantioselectivities. Synthetic transformations have been demonstrated, including the synthesis of functionalized 2,3-dihydrobenzofurans and 1-pyrroline.