Ruthenium-Catalyzed Cycloaddition of Propargylic Alcohols with Phenol Derivatives via Allenylidene Intermediates: Catalytic Use of the Allenylidene Ligand as the C₃ Unit

Novel ruthenium-catalyzed cycloaddition of propargylic alcohols with 2-naphthols and phenols bearing electron-donating groups via allenylidene intermediates has been developed to give the corresponding 1H-naphtho[2,1-b]pyrans and 4H-1-benzopyrans, respectively, in moderate to excellent yields with complete regioselectivity.