title: Acylammonium salts as dienophiles in Diels-Alder/lactonization organocascades.
abstract: α,β-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 γ- and δ-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.
authors.affiliation: Department of Chemistry, Texas A&M University , P.O. Box 30012, College Station, Texas 77842-3012, United States.
authors.forename: Mikail E
authors.initials: ME
authors.lastname: Abbasov
authors.forename: Brandi M
authors.initials: BM
authors.lastname: Hudson
authors.forename: Dean J
authors.initials: DJ
authors.lastname: Tantillo
authors.forename: Daniel
authors.initials: D
authors.lastname: Romo