A unique effect of styrene additive on product selectivity was observed for RuH2(CO)(PPh3)3-catalyzed C−H arylation of acetophenone derivatives bearing two ortho C−H bonds. Without styrene, the C−H arylation with arylboronates gives diarylation products as the major products throughout the reaction, but the use of styrene as an additive switches the product selectivity and leads to selective formation
RuHCl(CO)(PiPr3)2, CsF, and a styrene derivative was found to be applicable to selective monoarylation of aromatic ketones via ortho C-H bond cleavage. The reaction of 2'-methoxyacetophenone with arylboronates gave C-H arylation products without cleaving the ortho C-O bond. Acetophenone was also converted to monoarylation products with high selectivity. Cyclohexanone was found to be an effective solvent