CuCl2-promoted 6-endo-dig chlorocyclization and oxidative aromatization cascade: efficient construction of 1-azaanthraquinones from N-propargylaminoquinones.

An efficient synthetic methodology was developed to assemble 1-azaanthraquinones from N-propargylaminoquinones by copper(II)-promoted sequential 6-endo-dig chlorocyclization and oxidative aromatization. The approach can be extended to preprare chlorinated alkaloids such as cleistophine and sampangine. A possible mechanism involving carbon-carbon bond formation triggered by regioselective electrophilic activation and carbon-chlorine bond formation via reductive elimination was proposed.