Department of Chemistry, Northeast Normal University, Changchun 130024, China.
J Org Chem. 2009 Aug 21;74(16):6105-10. doi: 10.1021/jo9013386.
The regiospecific [5C + 1C] annulation of readily available alpha-alkenoyl ketene (S,S)-acetals 1 with aryl methyl ketones 2, the less active methylene compounds, has been developed. Upon treatment of 1 with 2 in the presence of t-BuOK in DMF at room temperature, highly substituted 2-cyclohexenones 3 were synthesized in high to excellent diastereoselectivities with high yields. On the basis of this strategy, sterically hindered benzophenones 4 were conveniently prepared via the iodonation-aromatization of 2-cyclohexenones 3 with I(2) in MeONa/MeOH basic medium. Furthermore, benzophenones 4 were also obtained directly from 1 and 2 following a sequential [5 + 1] annulation-iodonation-aromatization procedure in a one-pot operation.
已开发出通过易得的α-烯酰基酮缩硫醛（S，S）-缩醛 1 与芳基甲基酮 2（不太活泼的亚甲基化合物）进行区域选择性 [5C + 1C] 环合。在室温下 t-BuOK 的存在下，用 1 处理 2 时，高取代的 2-环己烯酮 3 以高至优异的非对映选择性和高收率合成。在此策略的基础上，通过 3 与 I(2)在 MeONa/MeOH 碱性介质中的碘化-芳构化，方便地制备了空间位阻的二苯甲酮 4。此外，通过在一锅操作中连续进行 [5 + 1] 环合-碘化-芳构化步骤，也可直接从 1 和 2 得到二苯甲酮 4。
