Zn(OTf)2-Catalyzed Cyclization of Proparyl Alcohols with Anilines, Phenols, and Amides for Synthesis of Indoles, Benzofurans, and Oxazoles through Different Annulation Mechanisms

Manyam Praveen Kumar and Rai-Shung Liu*
Department of Chemistry, National Tsing-Hua University, Hsinchu, Taiwan 30043
J. Org. Chem., 2006, 71 (13), pp 4951–4955
DOI: 10.1021/jo0606711
Publication Date (Web): May 23, 2006
Copyright © 2006 American Chemical Society
*

In papers with more than one author, the asterisk indicates the name of the author to whom inquiries about the paper should be addressed.

, rsliu@mx.nthu.edu.tw

Abstract

Abstract Image

Zn(OTf)2 (10 mol %) catalyzed the cyclization of propargyl alcohols with PhXH (X = O, NH) in hot toluene (100 οC) 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.

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History

  • Published In Issue June 23, 2006
  • Received March 28, 2006

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