Copper-catalyzed Cyclization of 3-Acylcoumarin Hydrazone using Air as the Oxidant: Efficient Synthesis of Pyrazole-Fused Coumarin Derivatives

摘要

An efficient, convenient Cu-catalyzed formation of chromeno[4,3-c]pyrazol-4(1H)-ones is reported. In this atom economic process, readily available 3-acylcoumarin hydrazone is oxidative cyclized by direct C-N bond formation. Air has been successfully used as an oxidant, which has important economic and environmental advantages. A broad scope of 3-acylcoumarin hydrazones can be utilized in this process.