Asymmetric Synthesis of 3,3-Diarylpropanals with Chiral Diene−Rhodium Catalysts

A general route to enantioenriched 3,3-diarylpropanals is presented. These useful building blocks are prepared via an asymmetric rhodium-catalyzed conjugate addition of arylboronic acids to cinnamaldehyde derivatives in the presence of chiral dienes. The addition of both electron-poor as well as electron-rich boronic acids proceeds smoothly with various enals in 63-90% yield with high enantioselectivities (89-93% ee).