Department of Chemistry, Scripps Florida, Jupiter, Florida 33458, USA.
Org Lett. 2012 Jun 15;14(12):3028-31. doi: 10.1021/ol3010968. Epub 2012 May 30.
Enantioselective hydroboration of racemic allenylboronate (±)-1 with 0.48 equiv of ((d)Ipc)(2)BH at -25 °C proceeds with efficient kinetic resolution and provides allylborane (R)-Z-4. When heated to 95 °C, allylborane (R)-Z-4 isomerizes to the thermodynamically more stable allylborane isomer (S)-E-7. Subsequent allylboration of aldehydes with (R)-Z-4 or (S)-E-7 at -78 °C followed by oxidative workup provides 1,2-syn- or 1,2-anti-diols, 2 or 3, respectively, in 87-94% ee.
外消旋烯丙基硼酸酯(±)-1与 0.48 当量的 ((d)Ipc)(2)BH 在-25°C下进行对映选择性硼氢化反应,反应具有高效的动力学拆分,并提供手性烯丙基硼烷(R)-Z-4。当加热至 95°C 时,手性烯丙基硼烷(R)-Z-4 异构化为热力学上更稳定的烯丙基硼烷异构体(S)-E-7。随后,(R)-Z-4 或(S)-E-7 在-78°C 下与醛进行烯丙基硼化反应,然后进行氧化处理,分别以 87-94%的对映体过量(ee)得到 1,2-顺式或 1,2-反式二醇 2 或 3。