Acylammonium Salts as Dienophiles in Diels-Alder/Lactonization Organocascades

Am. Chem. Soc., 2014, 136(12), pp 4492–4495.

Mikail E. Abbasov †, Brandi M. Hudson ‡, Dean J. Tantillo ‡, and Daniel Romo *†

  Department of Chemistry, Texas A&M University, P.O. Box 30012, College Station, Texas 77842-3012, United States and

 Department of Chemistry, University of California—Davis, One Shields Avenue, Davis, California 95616,United States.

 

Abstract

 

{Alpha},{Beta}-Unsaturated acylammonium salts, generated in situ from commodity acid chlorides and a chiral isothiourea organocatalyst, comprise a new and versatile family of chiral dienophiles for the venerable Diels–Alder (DA) cycloaddition. Their reactivity is unveiled through a highly diastereo- and enantioselective Diels–Alder/lactonization organocascade that generates cis– and trans-fused bicyclic {Gamma}- and {Delta}-lactones bearing up to four contiguous stereocenters. Moreover, the first examples of DA-initiated, stereodivergent organocascades are described delivering complex scaffolds found in bioactive compounds. The origins of stereoselectivity are rationalized through computational studies. In addition, the utility of this methodology is demonstrated through a concise approach to the core structure of glaciolide and formal syntheses of fraxinellone, trisporic acids, and trisporols.

Copyright © 2014 American Chemical Society.

 

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