Highly enantioselective Friedel–Crafts alkylation of indole and pyrrole with β,γ-unsaturated α-ketoester catalyzed by chiral dicationic palladium complex
The chiral dicationic Pd complexes, bearing sterically demanding diphosphine ligands as Lewis acid catalysts, are shown to catalyze the asymmetric Friedel–Crafts (F–C) alkylations of indoles and pyrroles with β,γ-unsaturated α-ketoesters, to provide the F–C alkylation products with benzylic stereocenters in high yields and enantioselectivities. The reactive chelated structure, formed by the chiral dicationic
You can count on the anion: Simply swapping the anions of an indium Lewis acid leads to a remarkable regioselectivity switch between asymmetric 1,2‐ and 1,4‐addition reactions. N‐protected indoles and β,γ‐unsaturated α‐keto esters gave adducts with excellent enantioselectivity (see scheme).