1,1-, 1,2-, and 1,4-Eliminations from the Corresponding Dihalogenated Compounds Using Bu_3SnSiMe_3-F^-

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We have already reported the generation of stannyl anion from Me_3SiSnBu_3 in the presence of CsF in DMF and the utilization of this stannyl anion for the novel cyclization via halogen-metal exchange reaction. It was expected that the active intermediates would be produced from the corresponding dihalo-compounds by 1,1-, 1,2-, or 1,4-elimination. At first, when alpha, alpha'-dibromo-o-xylene was treated with Me_3SiSnBu_3 and CsF in the presence of methyl acrylate in DMF,2-carbomethoxy tetrahydronaphthalene was obtained in 87% yield. In a similar manner, the various tetrahydronaphthalene derivatives were obtained in good yields. On the other hand, benzyne was produced from 1,2-dibromobenzene. This reaction was further developed for the generation of alkylidene carbene from 1,1-dibromoalkene, and we could obtained alkenes or cyclopentenone derivatives from the crresponding 1,1-dibromoalkene in good to moderate yields.