Electrogenerated-bases promoted electrochemical synthesis of N-bromoamino acids from imines and carbon dioxide

In this paper, the one-step synthesis of N-bromoamino acids has been developed by electrolyzing imines and carbon dioxide (4 MPa). The electrosynthesis was performed in an undivided cell with Ni cathode and Al sacrificial anode containing n-Bu4NBr-DMF as supporting electrolyte with a constant current at room temperature. The N-bromoamino acids were afforded in moderate to good yields rather than traditional a-amino acids. To explore the truth, some influenced factors (cathode materials, supporting electrolyte, and electricity etc.) were investigated. The experimental results indicated that the NH group of the alpha-amino acid could be deprotonated by alkyl anion R- (carbanion, a strong base), followed by the oxidation of hypobromous acid resulted from the two-step oxidation of the bromide ion at the anode, and produced the N-bromoamino acid. Finally, the reaction mechanism was briefly discussed. (C) 2014 Elsevier Ltd. All rights reserved.