Triflic Acid-Catalyzed Enynes Cyclization: A New Strategy beyond Electrophilic [pi]-Activation

• Published in: Chemistry : a European journal Vol. 22; no. 25; p. 8488
• Main Authors: Yu, Zhunzhun, Liu, Lu, Zhang, Junliang
• Format: Journal Article
• Language: English
• Published: Weinheim Wiley Subscription Services, Inc 13-06-2016
• Subjects: Chemistry
• ISSN: 0947-6539; 1521-3765
• DOI: 10.1002/chem.201601599

The cyclization of enynes, catalyzed by a transition metal, represents a powerful tool to construct an array of cyclic compounds through electrophilic π-activation. In this paper, we disclose a new and efficient strategy for enynes cyclization catalyzed by triflic acid. The salient features of this transformation includes a broad substrate scope, metal free synthesis, open flask and mild conditions, good yields, ease of operation, low catalyst loading, and easy scale-up to gram scale. A preliminary mechanism study demonstrated that the activation model of the reaction was σ-activation, which is different from the transition-metal-catalyzed enynes cyclization. Our strategy affords a complementary method to the traditional strategies, which use transition-metal catalysts.