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Investigation of oxidopyrylium-alkene [5+2] cycloaddition conjugate addition cascade (C3) sequences.
Chem Commun (Camb)
; 50(65): 9130-3, 2014 Aug 21.
Article
in English
| MEDLINE
| ID: mdl-24990799
ABSTRACT
Novel oxidopyrylium-alkene [5+2] cycloaddition conjugate addition cascade (C(3)) sequences are described. Various acetoxypyranone-alkenes with pendant nucleophiles undergo [5+2] cycloaddition followed by conjugate addition from the concave face of the intermediate pyranone toward bridged, tetracyclic ethers. In several cases, 3 new rings, 4 new bonds, and 6 new contiguous stereocenters are constructed with excellent diastereoselectivity. Finally, an asynchronous concerted reaction pathway is proposed to explain the high diastereoselectivity of the oxidopyrylium-alkene [5+2] C(3).