Allylation Reactions of Aldehydes with Allylboronates in Aqueous Media: Unique Reactivity and Selectivity that are Only Observed in the Presence of Water
作者:Shū Kobayashi、Toshimitsu Endo、Takumi Yoshino、Uwe Schneider、Masaharu Ueno
DOI:10.1002/asia.201300440
日期:2013.9
Zn(OH)2‐catalyzed allylation reactions of aldehydes with allylboronates in aqueous media have been developed. In contrast to conventional allylboration reactions of aldehydes in organic solvents, the α‐addition products were obtained exclusively. A catalytic cycle in which the allylzinc species was generated through a B‐to‐Zn exchange process is proposed and kinetic studies were performed. The key
已经开发了在水性介质中醛与烯丙基硼酸酯的Zn(OH)2催化的烯丙基化反应。与传统的醛在有机溶剂中的烯丙基硼化反应相反,α-加成产物是唯一获得的。提出了一个催化循环,其中烯丙基锌物质是通过B到Zn交换过程生成的,并进行了动力学研究。通过HRMS(ESI)分析和在线连续MS(ESI)分析检测了关键中间体烯丙基锌。该分析表明,在水性介质中,烯丙基锌物质与醛和水竞争性反应。用几种典型的烯丙基硼酸根(6a,图6b,6c,6d)阐明了水在该烯丙基化反应中的几个重要作用。醛与烯丙基硼酸2,2-二甲基-1,3-丙二醇酯的烯丙基化反应在水性介质中存在催化量的Zn(OH)2和非手性配体4d的情况下顺利进行,从而提供了相应的顺式加合物。具有非对映选择性高的收率。在所有情况下,均获得了α加成产物,并且可以耐受广泛的底物范围。此外,通过使用手性配体9将该反应应用于不对称催化。基于Zn- 9的X射线结构此外,还发现一