Catalytic asymmetric Friedel-Crafts alkylation of unprotected indoles with nitroalkenes using a novel chiral Yb(OTf)-pybox complex.

Chiral chloro-indeno pybox has served as a new ligand for the Yb(OTf)-catalyzed asymmetric Friedel-Crafts alkylation reaction of indoles with nitroalkenes. The tunable nature of pybox ligands enables the rational design of catalysts for optimal performance in terms of both activity and stereoselectivity in a Friedel-Crafts-type reaction. Good to excellent yields and enantioselectivities were obtained for a relatively wide range of substrates, including sterically hindered compounds, under optimized reaction conditions.