Benzofuran synthesis via copper-mediated oxidative annulation of phenols and unactivated internal alkynes

The first example of copper-mediated oxidative annulation of phenols and unactivated internal alkynes to afford benzofuran derivatives was reported. Various phenols and unactivated internal alkynes were successfully employed. Mechanistic studies disclosed a new strategy on annulations of alkynes with phenols through reversible electrophilic carbocupration of phenol followed by alkyne insertion and cyclization.