Directing/Protecting‐Group‐Free Synthesis of Tetraaryl‐Substituted Pyrazoles through Four Direct Arylations on an Unsubstituted Pyrazole Scaffold

Abstract

A directing/protecting-group-free synthesis of 1,3,4,5-tetraaryl-substituted pyrazoles was achieved through four transition metal-catalyzed direct arylations. Various pyrazoles with four different aryl rings were obtained using readily available reagents from an unsubstituted pyrazole. Two aryl-substituted pyrazoles showed intense violet fluorescence, high quantum yields (Φf =0.68, 0.64), and large Stokes shifts (19000, 15200 cm(-1) ).