The metal tin promoted cascade reaction of ketones in aqueous media for the construction of 2-bromo-4-aryl-1,3-pentadiene
作者:Lingyan Liu、Yan Zhang、Hua Zhang、Kaimeng Huang、Bo-xin Gao、Min Zou、Xin Zhou、Hongkai Wang、Jing Li
DOI:10.1039/c4ob00584h
日期:——
A novel Barbier-type allenylation cascade reaction of carbonyl compounds promoted by tin was discovered, and afforded a new, highly functionalized 1,3-pentadiene.
Studies on Electrophilic Reaction of Tertiary 2,3-Allenols with NBS in H<sub>2</sub>O or Aqueous MeCN: An Efficient Selective Synthesis of 2-Bromoallylic Ketones, 1,2-Allenyl Ketones, or 3-Bromo-2,5-dihydrofurans
作者:Jing Li、Wangqing Kong、Yihua Yu、Chunling Fu、Shengming Ma
DOI:10.1021/jo9018717
日期:2009.11.20
Previously, we observed that the electrophilic reaction of 2,3-allenols with X+ (X = Br, I) affords 3-halo-2-alkenals or 2-halo-2-alkenyl ketones in aqueous MeCN (MeCN/H2O = 15:1). However, the reaction of tertiary 2,3-allenols with NBS under these reaction conditions affords a mixture of rearrangement products (aldehydes or ketones) together with 1-bromovinyl epoxides in a low selectivity. Due to
以前,我们观察到2,3-烯醇与X +(X = Br,I)的亲电反应在水性MeCN(MeCN / H 2 O = 15:1)。然而,在这些反应条件下,叔2,3-烯醇与NBS的反应在低选择性下提供了重排产物(醛或酮)与1-溴乙烯基环氧化物的混合物。由于2-卤代烯丙基酮的合成潜力,我们决定进一步探索该反应。筛选后,我们观察到末端叔2,3-烯醇与NBS在水中的亲电反应可通过Br +的顺序亲电相互作用以高达97%的产率高度选择性地提供2-溴代烯丙基酮与丙二烯部分形成可能具有更取代的C═C键的三元溴中间体,然后进行1,2-芳基或1,2-烷基转移以打开应变的三元环并质子消除形成羰基官能团。当R 1和R 2(与羟基连接的碳原子上的取代基)均为烷基时,这两个基团之一迁移;当R 1和R 2都为烷基时,这两个基团之一被迁移。与1,2-丙二烯基环烷醇一起,观察到扩环反应。R 1是芳基,R 1将仅转移形成2-溴烯丙基酮。有趣的是,在用10滴Et
Zinc Amide Catalyzed Regioselective Allenylation and Propargylation of Ketones with Allenyl Boronate
Zinc amide catalyzed, regioselective allenylation and propargylation of ketones with allenyl boronate is reported. Tertiary allenyl and homopropargyl alcohols were obtained, respectively, in high selectivities, from the same starting materials, simply by changing the reaction conditions. The substrate scope was wide. Mechanistic studies suggest that the reactions are controlled under kinetic and thermodynamic conditions.