Investigation of Pd‐PEPPSI catalysts and coupling partners towards direct C2‐arylation/heteroarylation of benzoxazole.

2‐Aryl/heteroaryl‐substituted benzoxazoles are important heterocyclic motifs extensively found in several bioactive molecules, pharmaceuticals and natural products. In view of the importance of these compounds, there is need to develop easiest and simplest synthetic routes. The motive of this current work is to conduct the direct C2‐arylation reaction on benzoxazole with various cross‐coupling partners like aryl/heteroaryl halide/carboxylic acid/diazonium tetrafluoroborate/sulfonyl chloride/boronic acids in the presence of different symmetrical and unsymmetrical Pd‐PEPPSI (pyridine‐enhanced pre‐catalyst preparation by stabilization initiation) catalysts via C (sp2)–C (sp2) bond formation. Compared with other coupling partners, boronic acids coupled with benzoxazole very efficiently in the presence of sterically and electronically tunable bulky1,3‐bis(N,N′‐2,4,6‐triisopropylbenzyl)benzimidazolium‐Pd‐PEPPSI complex in open air to offer the corresponding C2‐aryl/heteroaryl benzoxazole compounds. Further, it is worthy to mention that there is no need of any external oxidant/ligand/additive for the complete conversion of starting molecules to products. The reactions progressed successfully with a wide range of substrate scope and attained the products in good to excellent yields in a short reaction time in ethanol/water (1:1) medium. Greatly, catalysts can be recovered and reused for few cycles with significant reactivity. [ABSTRACT FROM AUTHOR]