Rhodium(III)-catalyzed intermolecular cascade annulation through C-H activation: Concise synthesis of rosettacin

An intermolecular annulation of 2-acetylenic aldehydes or ketones with O-substituted N-hydroxybenzamides or N-hydroxyacrylamides through rhodium(III)-catalyzed C–H activation for the synthesis of isoquinolones and indolizinones is developed. This reaction features excellent functional-group tolerance and broad substrate scope, including annulation of various heterocyclic substrates. This approach evaluates the chemoselectivity of the reaction when sterically hindered diaryl-substituted alkynes are incorporated. This method also furnishes an efficient approach for the total synthesis of rosettacin and a topoisomerase I inhibitor. © 2018 Elsevier B.V.