Rh(III)-Catalyzed Cascade Annulations To Access Isoindolo[2,1-b]isoquinolin-5(7H)-ones via C-H Activation: Synthesis of Rosettacin.

An efficient protocol for the synthesis of diversely substituted 7-hydroxyisoindolo[2,1-b]isoquinolin-5(7H)-ones from the reaction of N-(pivaloyloxy)benzamides with 2-alkynyl aldehydes has been developed, which proceeds through sequential alkyne insertion followed by addition of the amide nitrogen on to the aldehyde. This method provided the products with aminal functionality as a handle for further diversification. The synthetic utility of this strategy was successfully illustrated by the concise, two-step synthesis of an alkaloid, rosettacin, and a topoisomerase I inhibitor.