Abstract
Zn(OTf) 2 (10 mol %) catalyzed the cyclization of propargyl alcohols with PhXH (X = O, NH) in hot toluene (100 °C) without additive and gave indole and benzofuran products with different structures. In such transformations, α-carbonyl intermediates A and C were isolated as reaction intermediates. The 1,2-nitrogen shift in the formation of indole is catalyzed by Zn(OTf) 2 , and its mechanism has been elucidated. This catalytic cyclization is also applicable to the synthesis of oxazoles through the cyclization of propargyl alcohols and amides without a 1,2-nitrogen shift. © 2006 American Chemical Society.