Copper-Free Asymmetric Allylic Alkylation with a Grignard Reagent: Design of the Ligand and Mechanistic Studies
作者:David Grassi、Chrysanthi Dolka、Olivier Jackowski、Alexandre Alexakis
DOI:10.1002/chem.201202318
日期:2013.1.21
The Cu‐free asymmetric allylic alkylation, catalysed by NHC, with Grignard reagents is reported on allyl bromide derivatives with good results. The enantioselectivity was quite homogeneous (around 85 % ee) on large and various substrates, regardless of the nature of the Grignard reagent. The formation of stereogenic quaternary centres was highly regioselective for both aliphatic and aromatic derivatives
据报道,NHC用格氏试剂催化的无铜不对称烯丙基烷基化反应对烯丙基溴衍生物具有良好的效果。不管格氏试剂的性质如何,在各种不同的底物上,对映选择性都相当均匀(约ee约为85% )。对于具有良好对映异构体过量(至多92%ee)的脂肪族和芳香族衍生物,立体构象的四元中心的形成具有高度的区域选择性 。发现开发的方法与铜催化的方法互补。测试了几种新的NHC,提高了效率。另外,使用NMR光谱的机理研究导致发现了催化活性物质。