(<i>S</i>)-(+)-<i>N</i>-Acetylphenylglycineboronic Acid: A Chiral Derivatizing Agent for Ee Determination of 1,2-Diols
作者:Emilia Caselli、Chiara Danieli、Stefania Morandi、Beatrice Bonfiglio、Arrigo Forni、Fabio Prati
DOI:10.1021/ol0359970
日期:2003.12.1
[GRAPHICS]A new chiral derivatizing agent for ee determination of 1,2-diols via H-1 NMR is described. (S)-(+)-N-Acetylphenylglycineboronic acid (1) is synthesized in enantiomerically pure form; its reaction with chiral diols quantitatively yields cyclic boronic esters 5a-g. The latter show a remarkably high diastereodifferentiation of proton NMR signals useful for de determination.
Inversion or Retention? Effects of Acidic Additives on the Stereochemical Course in Enantiospecific Suzuki–Miyaura Coupling of α-(Acetylamino)benzylboronic Esters
The stereochemicalcourse of the stereospecific Suzuki-Miyaura coupling of enantioenriched α-(acetylamino)benzylboronic esters with aryl bromides can be switched by the choice of acidic additives in the presence of a Pd/XPhos catalyst system. Highly enantiospecific, invertive C-C bond formation takes place with the use of phenol as an additive. In contrast, high enantiospecificity for retention of
在 Pd/XPhos 催化剂体系的存在下,可以通过选择酸性添加剂来切换对映体富集的 α-(乙酰氨基)苄基硼酸酯与芳基溴的立体定向 Suzuki-Miyaura 偶联的立体化学过程。使用苯酚作为添加剂可形成高度对映体的、倒置 CC 键。相比之下,在 Zr(Oi-Pr)(4)·i-PrOH 作为添加剂存在的情况下,实现了构型保留的高对映特异性。