Enantioselective Friedel–Crafts Alkylation of Indoles with ( E )‐1‐Aryl‐4‐benzyloxybut‐2‐en‐1‐ones Catalyzed by an ( R )‐3,3′‐Br 2 BINOLate–Hafnium(IV) Complex

A highly enantioselective Friedel–Crafts reaction of unprotected indoles with ( E )‐1‐aryl‐4‐benzyloxybut‐2‐en‐1‐ones catalyzed by a new chiral [Hf{( R )‐3,3′‐Br 2 ‐BINOL}(O t Bu) 2 ] 2 complex has been developed to functionalize the C‐3 position of the indole nucleus with a side chain bearing a 1,4‐difunctionalized moiety and a benzylic stereogenic center. The reaction proceeds in good to excellent yields and excellent enantioselectivities (up to 97 % ee ). The usefulness of this approach was illustrated with the synthesis of a tryptophol derivative.