Copper-Catalyzed Chan-Lam Reaction and Sequential [2,3]-Rearrangement to Prepare α-Benzotriazinium Ketones

A variety of alpha-benzotriazinium ketones were prepared in 38%-89% yields through a copper(II)-catalyzed Chan-Lam reaction and [2,3]-rearrangement in a one pot reaction open to air from N-hydroxybenzotriazin-4-ones and alkenyl boronic acids at room temperature. Experimental results showed that the copper catalyst not only played as cross-coupling catalyst but also served as Lewis acid catalyst to control the chemoselectivity of [2,3]-rearrangement. The reaction tolerated various linear and cyclic disubstituted alkenyl boronic acids. Moreover, alpha-benzotriazinium ketone could be easily prepared in gram scales. The present method highlights dual roles of copper catalyst and [2,3]-rearrangement of N,O-vinyl moiety.