Furan Ring Opening – Pyridine Ring Closure: An Efficient Approach towards 6H‐Isochromeno[4,3‐b]pyridin‐6‐ones from Readily Available Furans and Phthalaldehydic Acid Methyl Esters

An efficient iodine‐catalyzed three‐component Mannich‐type reaction of various 2‐alkylfurans, methyl 2‐formylbenzoates and carbamates under mild reaction conditions was realized. Synthetic utility of the resulting N‐Boc‐1‐[2‐(carbomethoxy)aryl]furfurylamines was demonstrated by their facile two‐step transformation into 2‐methyl‐6H‐isochromeno[4,3‐b]pyridin‐6‐ones, which are employed in high‐performance cyclometalated OLEDs. Straightforward functionalization of furans by means of a three‐component Mannich‐type condensation reaction with methyl 2‐formylbenzoates and carbamates was accomplished. The synthetic utility of the resultant N‐Boc arylfurfurylamines was demonstrated by a practical two‐step strategy that leads to 6H‐isochromeno[4,3‐b]pyridin‐6‐ones, which are used as cyclometalating ligands for OLEDs.