Copper-Catalyzed Cross Dehydrogenative Coupling of N,N-Disubstituted Formamides and Phenols: A Direct Access to Carbamates

An efficient copper-catalyzed protocol has been developed for the synthesis of carbamates from dialkylformamides and phenols possessing directing groups such as benzothiazole, quinoline and formyl at the ortho-position. In this chelation assisted approach, C O bond formation takes place via a cross dehydrogenative coupling (CDC) between the formyl C-H of dialkylformamide and phenolic O-H in the presence of copper(II) acetate/aqueous tertbutyl hydroperoxide. Under identical reaction conditions, salicylic acid derivatives underwent amidation with the carboxylic group rather than formamidation of the phenolic OH. The use of a cheap and environmentally benign catalyst along with the tolerance of a wide range of functional groups makes this an easy, phosgene-free route to carbamates.