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Pure Appl. Chem., 2011, Vol. 83, No. 3, pp. 507-518

http://dx.doi.org/10.1351/PAC-CON-10-09-06

Published online 2011-01-18

New samarium diiodide-induced cyclizations

Christine Beemelmanns and Hans-Ulrich Reissig*

Institute for Chemistry and Biochemistry, Freie Universität Berlin, Takustr. 3, D‑14195 Berlin, Germany

Abstract: Samarium diiodide (SmI2) smoothly promotes the cyclizations of suitably substituted carbonyl compounds with styrene subunits leading to benzannulated cyclooctenes. The intramolecular samarium ketyl addition to arene or hetarene moieties enables a new, efficient, and highly stereoselective entry to dearomatized products such as hexahydronaphthalenes, steroid-like tetra- or pentacyclic compounds, or dihydroindole derivatives. The usefulness of the developed SmI2-induced cyclization method was demonstrated by the shortest formal total synthesis of the alkaloid strychnine.