One-Pot, Catalyst-Free Synthesis of Spiro[dihydroquinoline-naphthofuranone] Compounds from Isatins in Water Triggered by Hydrogen Bonding Effects

A one-pot, catalyst-free route to spiro[dihydroquinoline-naphthofuranone] compounds from isatins through ring-opening and cyclization processes in water is disclosed. Hydrogen-bonding effects of water proved to be the key factor to accelerate the transformation. In addition, the chemistry provides several advantages including that it is free of organic solvents, a simple operation, and a gram-scale synthesis and uses inexpensive reagents and a recyclable reaction medium.