Asymmetric Friedel–Crafts Alkylation of α‑Substituted β-Nitroacrylates: Access to β^2,2-Amino Acids Bearing Indolic All-Carbon Quaternary Stereocenters

A highly enantioselective Friedel–Crafts alkylation reaction of indoles with acyclic α-substituted β-nitroacrylates is developed under the catalysis of Ni­(ClO₄)₂–bisoxazoline complex at 1 mol % catalyst loading, affording chiral indolic β-nitroesters bearing all-carbon quaternary stereocenters in excellent yields and ees of up to 97%. Transformation of one of the products to β^2,2-amino ester and tetrahydro-β-carboline through nitro reduction and sequential Pictet–Spengler cyclization was exemplified