New adaptive chiral thiophene ligands for copper-catalyzed asymmetric reaction

A new type of adaptive chiral thiophene-based ligands 3 has been designed and developed. The synthetic flexibility of the thienyl ring allowed for the preparation of polydendate C2-symmetric ligands in good yields, carrying simultaneously ‘‘hard’’ as well as ‘‘soft’’ coordinating atoms (i.e., N, S). The coordination attitude of 3 was then tested in the enantioselective base-free Cu(OAc)2-catalyzed addition of nitromethane to aromatic aldehydes, leading to the corresponding b-nitro alcohols in excellent yields and enantiomeric excesses up to 86%.