Gold-catalyzed cyclization of (ortho-alkynylphenylthio)silanes:: Intramolecular capture of the vinyl-Au intermediate by the silicon electrophile

The gold-catalyzed cyclization of (ortho-alkynylphenylthio)si lanes 1 produced the corresponding 3-silylbenzo[b]thiophenes 2 in good to excellent yields. For example, the reaction of [2-(1-pentynyl)phenylthio]triisopropylsilane 1a, [2-(p-anisylethynyl)phenylthio]triisopropylsilane 1e, and (2-(phenylethynyl)phenylthio]triisopropyl si lane 1g in the presence of 2 mol % of AuCl in toluene at 45 degrees C gave 2a, 2e, and 2g in 98, 99, and 97% yields, respectively. This reaction proceeds through intramolecular capture of the vinyl-Au intermediate by the silicon electrophile, so-called silyldemetalation.