Controlled gold-catalyzed 5- <i>exo-dig</i> cyclization of 3-sulfur-substituted 1,3-dien-5-ynes for synthesizing fulvenes and the <i>in situ</i> reaction with indoles

Densely substituted fulvenes have been synthesized from 1,3-dien-5-ynes by gold-catalyzed 5-<i>exo-dig</i> cyclization, determined by the S-substituent. In addition, these fulvenes interact with the gold catalyst, forming fulvenium intermediates that react with indoles in a one-pot two-step protocol to synthesize 3-(alkylidene-cyclopent-2-en-1-yl)-1<i>H</i>-indoles, by the cooperative action of gold and Brønsted acid catalysts.