Benzoisothiazolone Organo/Copper-Cocatalyzed Redox Dehydrative Construction of Amides and Peptides from Carboxylic Acids using (EtO)₃P as the Reductant and O₂ in Air as the Terminal Oxidant

Carboxylic acids and amine/amino acid reactants can be converted to amides and peptides at neutral pH within 5–36 h at 50 °C using catalytic quantities of a redox-active benzoisothiazolone and a copper complex. These catalytic “oxidation–reduction condensation” reactions are carried out open to dry air using O2 as the terminal oxidant and a slight excess of triethyl phosphite as the reductant. Triethyl phosphate is the easily removed byproduct. These simple-to-run catalytic reactions provide practical and economical procedures for the acylative construction of C–N bonds.