ChemInform Abstract: Preparation and Reaction of Lanthanide(II) Trifluoromethanesulfonates.

Abstract

Preparation and Reaction of Lanthanide(II) Trifluoromethanesulfonates.-Samarium-promoted reductive coupling of acetophenone (I) yielding the pinacol (II) is investigated. Whereas a Sm(III)/Sm(0)-catalyst does not give any reaction (entry A), samarium(II) triflate generated in situ from samarium(III) triflate and ethylmagnesium bromide gives excellent yields (entry B and C). Other Grignard reagents such as iPrMgBr, tBuMgCl, or MeMgBr are less effective. Application of the samrium(II)-coupling conditions to the carbonyl compounds (III) leads to the formation of the diols (IV). For benzophenone (IIId), only the ytterbium(II) triflate-catalyzed reaction provides the desired pinacol (IVd). -(HANAMOTO, T.; SUGIMOTO, Y.; SUGINO, A.; INANAGA, J.; Synlett (1994) 5, 377-378; Inst. Mol. Sci., Myodaiji, Okazaki 444, Japan; EN)