title: Triflic Acid-Catalyzed Enynes Cyclization: A New Strategy beyond Electrophilic π-Activation.
abstract: 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.
authors.affiliation: Shanghai Key Laboratory of Green Chemistry and Chemical Processes, School of Chemistry and Molecular Engineering, East China Normal University, 3663 North Zhongshan Road, Shanghai, 200062, P. R. China.
authors.forename: Zhunzhun
authors.initials: Z
authors.lastname: Yu
authors.affiliation: Shanghai Key Laboratory of Green Chemistry and Chemical Processes, School of Chemistry and Molecular Engineering, East China Normal University, 3663 North Zhongshan Road, Shanghai, 200062, P. R. China. lliu@chem.ecnu.edu.cn.
authors.forename: Lu
authors.initials: L
authors.lastname: Liu
authors.affiliation: Shanghai Key Laboratory of Green Chemistry and Chemical Processes, School of Chemistry and Molecular Engineering, East China Normal University, 3663 North Zhongshan Road, Shanghai, 200062, P. R. China. jlzhang@chem.ecnu.edu.cn.|State Key Laboratory of Organometallic Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, 354 Fenglin Road, Shanghai, 200032, P. R. China. jlzhang@chem.ecnu.edu.cn.
authors.forename: Junliang
authors.initials: J
authors.lastname: Zhang
keywords: enynes; organic chemistry; synthetic methods; triflic acid; σ-activation