Catalytic Enantioselective Allylboration of Ketones

The first example of catalytic enantioselective allylboration and crotylboration of simple ketones is described. High enantioselectivity (up to 93% ee) was obtained using 3 mol % CuF-iPr-DuPHOS as a chiral catalyst and 4.5 mol % La(OiPr)3 as a cocatalyst. Mechanistic studies strongly suggested that the active nucleophile of the present reaction is an allylcopper, and that La(OiPr)3 facilitates the generation of an active allylcopper from the allylboronate, without affecting the transition-state structure of the ketone allylation step.