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.