Nickel-catalyzed C-H arylation of benzoxazoles and oxazoles: Benchmarking the influence of electronic, steric and leaving group variations in phenolic electrophiles

Electronic, steric and leaving group effects for Ni-catalyzed direct arylations using C-O electrophiles were benchmarked. The scope of arylations with pivalates was general with respect to both the electronics on the electrophile and the azoles. Furthermore, the arylation of azoles with tosylates, mesylates and carbamates with varying electronics was explored, and showed electronic trends similar to those of the pivalate reactions. Finally, the relative rate of arylation of 5-methyl benzoxazole with two electronically-similar electrophiles bearing different leaving groups was established. The results from these studies implicate the following order of relative reactivity: mesylates > pivalates > carbamates. (C) 2017 Elsevier Ltd. All rights reserved.