Highly tunable anionic tethered N-heterocyclic carbene of Pd(II) complexes for asymmetric allylic alkylation reaction
作者:Hiroshi Shirasaki、Miaki Kawakami、Haruka Yamada、Ryuichi Arakawa、Satoshi Sakaguchi
DOI:10.1016/j.jorganchem.2012.12.015
日期:2013.2
combination of [Pd(allyl)Cl]2 and the azolium salt 9, containing a 3-pentyl group at N(3) position in the NHC ring, efficiently promoted the AAA reaction to afford the corresponding alkylated product 7 with 67% ee. Furthermore, it was found that the Pd/NHC ratio was an important factor; the AAA reaction with a Pd/NHC ratio of 1:1 took place smoothly, whereas utilization of a Pd/NHC ratio of 1:2 resulted
研究了阴离子束缚的NHC配体体系在Pd催化的烯丙基不对称烷基化(AAA)反应中的多功能性。定义明确的阴离子酰胺化物/ NHC-Pd(II)络合物催化1,3-二苯基丙-3-烯-1-基乙酸酯(5)与NaCH(CO 2 Me)2的AAA反应。同样,通过使用原位生成的NHC-Pd(II)配合物发生AAA反应。各种NHC配体前体的筛选显示[Pd(烯丙基)Cl] 2和重氮盐9的组合有效地促进了AAA反应,该重氮盐9在NHC环的N(3)位置含有一个3-戊基。得到相应的烷基化产物7拥有67%的ee。另外,发现Pd / NHC比是重要的因素。Pd / NHC比为1:1的AAA反应顺利进行,而Pd / NHC比为1:2的利用可能导致底物的转化率较低,这可能是由于形成了催化惰性的bis(NHC)–Pd (二)情结。事实上,一项独立的实验表明,双(NHC)-Pd(II)络合物是通过用两当量的NHC-Ag络合物处理[Pd(烯丙基)Cl]