Mercuric Triflate·3TMU Catalyzed Cyclization of ω-Alkynoic Acids and Synthesis of a Naturally Occurring γ-Methylene-γ-lactone - Imagawa, Hiroshi; Fujikawa, Yukari; Tsuchihiro, Atsushi; Kinoshita, Atsushi; Yoshinaga, Takayuki; Takao, Hiroko; Nishizawa, Mugio (Synlett, 2006)