Visible-Light-Promoted Site-Selective N1-Alkylation of Benzotriazoles with α-Diazoacetates.

A visible-light-promoted highly site-selective N1-alkylation of benzotriazoles with diazo compounds has been achieved under mild and metal-free conditions. Using cheap, readily available p-benzoquinone (PBQ) as a catalyst, a wide range of benzotriazoles and diazo compounds are reacted, providing N1-alkylated benzotriazoles in moderate to excellent yields with excellent N1-selectivities. Preliminary mechanistic studies suggest that a radical process accounts for the exclusive site-selectivity of this transformation.