Copper-Catalyzed Tandem O-Arylation-Oxidative Cross Coupling: Synthesis of Chromone Fused Pyrazoles.

Intermolecular tandem copper-catalyzed O-arylation-oxidative acylation (cross dehydrogenative coupling-CDC) has been developed under air as an oxidant. The reaction between 2,4-dihydro-3H-pyrazol-3-ones and ortho-halo aryl carboxaldehydes furnished the corresponding chromone fused pyrazoles, in a straightforward manner. The synthetic utility of the presented tandem catalysis has been demonstrated with the synthesis of an A2-subtype selective adenosine receptor antagonist in only two steps.