Para-Selective, Iridium-Catalyzed C–H Borylations of Sulfated Phenols, Benzyl Alcohols, and Anilines Directed by Ion-Pair Electrostatic Interactions

Abstract

Para C-H borylations (CHB) of tetraalkylammonium sulfates and sulfamates have been achieved using bipyridine-ligated Ir boryl catalysts. Selectivities can be modulated by both the length of the alkyl groups in the tetraalkylammonium cations and the substituents on the bipyridine ligands. Ion pairing, where the alkyl groups of the cation shield the meta C-H bonds in the counter-anions, is proposed to account for para selectivity. The 4,4'-dimethoxy-2,2'-bipyridine ligand gave superior selectivities.