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

Abstract

Densely substituted fulvenes have been synthesized from 1,3-dien-5-ynes by gold-catalyzed 5-exo-dig 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-(alkylidenecyclopent-2-en-1-yl)-1H-indoles, by thecooperative action of gold and Brønsted acid catalysts.