-selective C-H arylation of phenols with -carboxyindoles under Brønsted acid- or Cu(i)-catalysis.

Control over chemo- and regioselectivity is a critical issue in the heterobiaryl synthesis C-H oxidative coupling. To address this challenge, a strategy to invert the normal polarity of indoles in the heterobiaryl coupling was developed. With -carboxyindoles as umpoled indoles, an exclusively -selective coupling with phenols has been realized, employing a Brønsted acid- or Cu(i)-catalyst (as low as 0.01 mol%). A range of phenols and -carboxyindoles coupled with exceptional efficiency and selectivity at ambient temperature and the substrates bearing redox-active aryl halides (-Br and -I) smoothly coupled in an orthogonal manner. Notably, preliminary examples of atropselective heterobiaryl coupling have been demonstrated, based on a chiral disulfonimide or a Cu(i)/chiral bisphosphine catalytic system. The reaction was proposed to occur through S2' substitution or a Cu(i)-Cu(iii) cycle, with Brønsted acid or Cu(i) catalysts, respectively.