Synthesis of Fused Pyrimido[1,6-a]indolones via Rhodium(III)-Catalyzed Cascade Annulations

Abstract A novel method for the synthesis of fused pyrimido[1,6- a ]-indolone derivatives by annulation of 2-alkynylaryl aldehydes/2-alkynyl­arylidene ketones with N -(pivaloyloxy)-1 H -indole-1-carboxamide catalyzed by rhodium has been accomplished. The reaction proceeds through C–H activation based annulation with alkyne moiety followed by addition of nitrogen on to aldehyde/activated alkene to give the products in moderate to good yields. Highly fluorescent dipyrrinone analogues could be synthesized from the derived products.