Gold-catalyzed reactions have been rapidly gained great importance as a synthetic method in organic chemistry. For a large part of gold-catalyzed reaction, the catalytic cycle is completed by trap of vinyl-Au intermediates with proton, so-called protodemetalation (Scheme 1, type a). Recently, several groups including ourselves have disclosed that such intermediates can also be captured by carbon electrophiles, such as iminium, α-alkoxyalkyl, allyl, and benzyl groups, in an intramolecular fashion (type b). We also recently reported that the vinyl-Au intermediate is trapped by sulfur electrophiles in our gold-catalyzed intramolecular aminosulfonylation reaction (type c). Now, we report that the vinyl-Au intermediate is intramolecularly captured by the silicon electrophiles (type d); gold-catalyzed cyclization of (ortho-alkynylphenylthio)silanes 1 produced 3-silylbenzo[b]thiophenes 2 in good to excellent yields (eq 1).
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