1999 reduction, hydrogenation reduction, hydrogenation O 0220 51 - 051 Metallic Samarium Promoted Reductive Dimerization Cycliza- tion of gem-Diactivated Alkenes, Reductive Debromination of vic-Dibromides, and Reduction of Sodium Alkyl Thiosulfates in Aqueous Media. — Metallic powdered samarium in aqueous solution (saturated aq. NH 4 Cl–THF) is shown to be a useful reducing agent not only in the reductive cyclodimerization of various gem-diactivated alkenes (I) and (IV), but also in the reduction of title thiosulfates (VI) as well as the dehalogenation of vic-dibromides like (VIII) and (X). The reactions proceed under mild conditions (aqueous solution, room temperature). Additionally, in the reductive cyclodimerization of amides (IVa)–(IVc) the trans,trans-adduct is obtained exclusively, and in the corresponding cyclization of esters (IVd)–(IVg) the trans,trans-adducts are formed with at least 80% diastereoselectivity. — (WANG, LEI; ZHANG, YONGMIN; Tetrahedron 55 (1999) 35, 10695-10712; Dep. Chem., Zhejiang Univ., Hangzhou 310027, Peop. Rep. China; EN) 1

ChemInform Abstract: Metallic Samarium Promoted Reductive Dimerization Cyclization of gem-Diactivated Alkenes, Reductive Debromination of vic-Dibromides, and Reduction of Sodium Alkyl

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Page 1: ChemInform Abstract: Metallic Samarium Promoted Reductive Dimerization Cyclization of gem-Diactivated Alkenes, Reductive Debromination of vic-Dibromides, and Reduction of Sodium Alkyl

1999 reduction, hydrogenation

reduction, hydrogenationO 0220

51 - 051Metallic Samarium Promoted Reductive Dimerization Cycliza-tion of gem-Diactivated Alkenes, Reductive Debromination ofvic-Dibromides, and Reduction of Sodium Alkyl Thiosulfates inAqueous Media. — Metallic powdered samarium in aqueous solution(saturated aq. NH4Cl–THF) is shown to be a useful reducing agent notonly in the reductive cyclodimerization of various gem-diactivated alkenes (I)and (IV), but also in the reduction of title thiosulfates (VI) as well as thedehalogenation of vic-dibromides like (VIII) and (X). The reactions proceedunder mild conditions (aqueous solution, room temperature). Additionally, inthe reductive cyclodimerization of amides (IVa)–(IVc) the trans,trans-adduct isobtained exclusively, and in the corresponding cyclization of esters (IVd)–(IVg)the trans,trans-adducts are formed with at least 80% diastereoselectivity. —(WANG, LEI; ZHANG, YONGMIN; Tetrahedron 55 (1999) 35, 10695-10712;Dep. Chem., Zhejiang Univ., Hangzhou 310027, Peop. Rep. China; EN)