The Improved <i>para</i>-Selective C(sp²)-H Borylation of Anisole Derivatives Enabled by Bulky Lewis Acid

Abstract

An improved para-selective C(sp2)-H borylation of anisole derivatives is described. The selective borylation is probably dominated by the change in electron density on the aromatic ring when a Lewis acid is coordinated with an anisole substrate. In addition, a sterically hindered bipyridyl ligand used in the reaction also favors para-selectivity. With this strategy, it has been demonstrated that the ratio of para-borylated products could be dramatically improved. The reaction proceeds at a milder temperature, and most substrates display moderate to good site-selectivity.

Keywords

• C-H borylation
• regioselectivity
• iridium-catalyst
• Lewis acid-base interaction