Samarium(II) Triflate as a New Reagent for the Grignard-Type Carbonyl Addition Reaction
作者:Shin-ichi Fukuzawa、Keisuke Mutoh、Teruhisa Tsuchimoto、Tamejiro Hiyama
DOI:10.1021/jo960260s
日期:1996.1.1
On treatment of a THF solution of Sm(OTf)(3) with 1 equiv of an organolithium or organomagnesium reagent-at ambient temperature, the purple or deep green solution of the divalent samarium triflate [Sm(OTf)(2)] was readily obtained. For this preparation, s-BuLi was the most effective as was evidenced by the reduction of a-phenylethyl iodide in the presence of HMPA. The Sm(OTf)(2) reagent mediated the Grignard-type reaction effectively in THF/HMPA; alkylation and allylation of ketones or aldehydes with alkyl, allyl, or benzyl halides proceeded via organosamarium intermediates. Diastereoselectivity of the samarium-Grignard reaction was examined using 2-methylcyclohexanone, 4-tert-butylcyclohexanone, and 2-phenylpropanal and was found to be higher in each case than that with SmI2. With 2-methylcyclohexanone, for example, Sm(OTf)(2) gave the greatest ratio of axial alcohol:equatorial alcohol = 99:1, and SmI2 gave a ratio of 91:9. Halides containing an ester or a silyl group were reactive in the Reformatsky- or Peterson-type reaction, respectively, using the Sm(OTf)(2) reagent.