Chemical libraries via sequential C-H functionalization of phenols

Phenols provide a useful template for diversification via sequential hydroarylation reactions. Specifically, a protocol has been developed that begins with the hydroarylation of cinnamic acids by 3,5-dimethoxyphenol to produce dihydrocoumarins. This activated ester undergoes facile ring-opening with amines to form a C-N bond and regenerate a phenol. The resulting phenol can be further functionalized via a second hydroarylation reaction. Thus, in 3-4 steps, a phenol is coupled with a cinnamic acid, an amine, and a cinnamic or propiolic acid.