A Rh(ii)/phosphoric acid co-catalyzed three-component reaction of diazo-ketones with alcohols and azonaphthalenes: access to indole derivatives via a formal [3 + 2]-cycloaddition.

A novel dearomatization/rearomatization/cyclization oxonium ylide trapping process is well developed via a dirhodium(ii) acetate and phosphoric acid cooperatively catalyzed multi-component reaction of diazo-ketones with alcohols and azonaphthalenes. This protocol provides an efficient route to synthesize N-substituted 1-amino-indole derivatives in good yield under mild reaction conditions.