A New Samarium Diiodide Induced Reaction: Intramolecular Attack of Ketyl Radical Anions on Aryl Substituents with Formation of 1,4-Cyclohexadiene Derivatives
Beware of samariumdiiodide and aryl ketones! If the ketyl radical anion which is formed by electron transfer finds a properly placed aryl group, a highly diastereoselective cyclization may occur. After the transfer of a second electron and protonation bi- and polycyclic products with a common 1,4-cyclohexadiene moiety may be isolated [Eq. (a)]. X=CHCO2 R, NCH2 Ph; HMPA=(Me2 N)3 PO.
作者:Hans-Ulrich Reißig、Faiz Ahmed Khan、Regina Czerwonka、Chimmanamada U. Dinesh、Aarif L. Shaikh、Reinhold Zimmer
DOI:10.1002/ejoc.200600360
日期:2006.10
A series of γ-oxo esters 27-34 was prepared from methyl 2-silyloxycyclopropanecarboxylates 1-9 as key building blocks in a flexible modular synthesis. Their samarium diiodide promoted cyclization to benzannulated cyclooctanol derivatives was systematically investigated. Samarium ketyl compounds derived from aldehydes 27 and 28 mainly provided tricyclic γ-lactones 38 and 39 as a result of a cis-selective