Copper-Catalyzed Regio- and Enantioselective Addition of Silicon Grignard Reagents to Alkenes Activated by Azaaryl Groups.

A new application of silicon Grignard reagents in C(sp3 )-Si bond formation is reported. With the aid of BF3 ⋅OEt2 , these silicon nucleophiles add across alkenes activated by various azaaryl groups under copper catalysis. An enantioselective version employing benzoxazole-activated alkenes as substrates and a CuI-josiphos complex as catalyst has been developed, forming the C(sp3)-Si bond with good to high enantiomeric ratios (up to 97:3). The method expands the toolbox for "conjugate addition" type C(sp3 )-Si bond formation.