An Efficient One-Pot Synthesis of Densely Functionalized Fused-Quinolines via Sequential Ugi4CC and Acid-Mediated Povarov-Type Reaction

A divergent synthesis of fused-quinolines has been explored by performing Ugi four-component condensation and sulfuric acid promoted deprotection/Povarov-type reaction in one-pot. The process involves Ugi condensation of propiolic acids, aldehydes/ketones, aminoaldehyde acetals and isocyanides followed by sulfuric acid promoted deprotection and Povarov-type reaction with anilines in ethanol. This method enables straightforward access to the structurally diverse 2,3-dihydro-1H-pyrrolo­[3,4-b]­quinolin-1-ones (DHPQ), 3,4-dihydrobenzo­[b]­[1,6]­naphthyridin-1­(2H)-ones (DHBN), and 2,3,4,5-tetrahydro-1H-azepino­[4,3-b]­quinolin-1-ones (THAQ), starting from readily available starting materials.