One-Pot Synthesis of d-Phenylalanine-Functionalized Multiwalled Carbon Nanotubes: A Metal-Free Chiral Material for the Asymmetric Electroreduction of Aromatic Ketones

A simple protocol to synthesize d-phenylalanine (d-PHE)-functionalized multiwalled carbon nanotubes (MWCNTs) via the one-pot method was established by grafting d-PHE onto MWCNTs to obtain d-PHE-MWCNTs under mild reaction conditions. The resulting d-PHE-MWCNTs were characterized in detail via spectroscopy and surface analysis. The electroreduction of 2,2,2-trifluoroacetophenone at the d-PHE-MWCNTs cathode afforded ( S)-α-(trifluoromethyl) benzyl alcohol whose yield was 65% and the enantiomeric excess was 40%. No extra catalysts were required in this electrochemical reaction solution compared with other reactions requiring homogeneous catalysis. The metal-free chiral material also showed acceptable asymmetric electroreduction performance, considerable stability, and favorable reusability.