Synthesis of 2-Acylphenol and Flavene Derivatives from the Ruthenium-Catalyzed Oxidative C-H Acylation of Phenols with Aldehydes.

The cationic ruthenium hydride complex [(C6H6)(PCy3)(CO)RuH](+)BF4 (-) has been found to be an effective catalyst for the oxidative C-H coupling reaction of phenols with aldehydes to give 2-acylphenol compounds. The coupling of phenols with α,β-unsaturated aldehydes selectively gives the flavene derivatives. The catalytic method mediates direct oxidative C-H coupling of phenol and aldehyde substrates without using any metal oxidants or forming wasteful byproducts.