Pd- and Rh-catalyzed hydroarylation of γ-(2-methoxycarbonylphenyl)propargylic alcohols: approaches to 4- or 5-substituted seven-membered benzolactones and 3,3-disubstituted phthalides

A study of the palladium-catalyzed hydroarylation/hydrovinylation reaction of γ-(2-methoxycarbonylphenyl)- propargylic alcohols with aryl iodides/vinyl triflates and of the rhodium-catalyzed one with organoboron derivatives is described. The opposite regiochemical outcome of the two processes allows an easy selective approach to 5- or 4-substituted benzoxepin- 1(3H)-ones by combining the hydroarylative/hydrovinylative step with cyclocondensation between −OH and −COOMe groups in the intermediate γ,γ-disubstituted or β,γ-disubstituted allylic alcohols. A one-flask procedure to give benzo[c]oxepin-1(3H)- ones directly from the starting alkyne has been also developed. Treatment of crude γ,γ-disubstituted allylic alcohols with NaOH, followed by acidification, affords 3,3-disubstituted phthalides.