I2-Mediated Iodobenzannulation of Yne-Allenones toward 1-Naphthols and Their Synthetic Application

A new I2-mediated iodobenzannulation of yne-allenones has been established, enabling breaking/rearranging of C≡C bonds to selectively access 4-iodonaphthalen-1-ols with generally good yields. The resulting 4-iodonaphthalen-1-ols could serve as a new and reliable coupling reagent, which further reacted with H2O under the oxygen conditions to generate unexpected 1,2-carbonyls with good yields through Pd-catalyzed deiodinated carbonylation, whereas employment of benzene-1,2-diamine as the nucleophile rendered 3-(quinoxalin-2-yl)naphthalen-1-ols through Pd-catalyzed [4 + 2] heterocyclization. On the basis of the controlled experiments, the mechanism for forming 1,2-carbonyls was proposed, including an oxidative addition, 1,3-palladium migration, reductive elimination, and oxidative dehydrogenation sequence.