Palladium(II)-catalyzed annulation of alkynes with ortho-ester-containing phenylboronic acids.

Palladium(II) catalyzes annulation of internal alkynes with methyl 2-boronobenzoate and (2-boronophenyl)acetate to provide 2,3-disubstituted indenones and 3,4-disubstituted 2-naphthols, respectively. The annulation reaction would proceed through transmetalation of Pd(II) with the boron reagents and insertion of the alkynes, followed by unprecedented 1,2-addition of the generated alkenylpalladium(II) species to the intramolecular ester group.