Synthesis of 4-quinolones via a carbonylative Sonogashira cross-coupling using molybdenum hexacarbonyl as a CO source.

A palladium-catalyzed CO gas-free carbonylative Sonogashira/cyclization sequence for the preparation of functionalized 4-quinolones from 2-iodoanilines and alkynes via two different protocols is described. The first method (A) yields the cyclized products after only 20 min of microwave (MW) heating at 120 °C. The second method (B) is a gas-free one-pot two-step sequence which runs at room temperature, allowing the use of sensitive substituents (e.g., nitro and bromide groups). For both protocols, molybdenum hexacarbonyl was used as a solid source of CO.