Zinc-Catalyzed Reactions of Ethenetricarboxylates with 2-(Trimethylsilylethynyl)anilines Leading to Bridged Quinoline Derivatives

Zinc Lewis acid-catalyzed cyclization of ethenetricarboxylate derivatives 1 with 2-ethynylanilines has been examined. Reaction of 1,1-diethyl 2-tert-butyl ethenetricarboxylate 1b with 2-(trimethylsilylethynyl)aniline substrates in the presence of Zn(OTf)(2) gave bridged quinoline derivatives in 43-85% yield. The reaction of 1b with 2'-aminoacetophenone also gave the bridged quinoline derivative in 41% yield. Thermal reaction of bridged quinolines (180-190 degrees C) afforded indole derivatives in moderate to good yields.