2,2′-Bipyridine-α,α′-trifluoromethyl-diol ligand: synthesis and application in the asymmetric Et<sub>2</sub>Zn alkylation of aldehydes
作者:Samuel Lauzon、Thierry Ollevier
DOI:10.1039/d1cc04556c
日期:——
A chiral 2,2′-bipyridine ligand (1) bearing α,α′-trifluoromethyl-alcohols at 6,6′-positions was designed in five steps affording either the R,R or S,S enantiomer with excellent stereoselectivities, i.e. 97% de, >99% ee and >99.5% de, >99.5% ee, respectively. The key step for reaching high levels of stereoselectivity was demonstrated to be the resolution of the α-CF3-alcohol using (S)-ibuprofen as the
手性 2,2'-联吡啶配体 ( 1 ) 在 6,6'-位带有 α,α'-三氟甲基-醇,分五步设计,得到具有优异立体选择性的R , R或S , S对映异构体,即97 % de, >99% ee 和 >99.5% de, >99.5% ee。已证明达到高立体选择性的关键步骤是使用 ( S )-布洛芬作为拆分剂拆分α-CF 3 -醇。2,2'-联吡啶-α,α'-CF 3 -二醇配体的初步应用在 Zn II 中得到了强调-催化芳香、杂芳香和脂肪醛的不对称乙基化反应。新开发的配体的协同电子缺陷和空间位阻特性使相应的醇具有良好的收率(高达 99%)和对映选择性(高达 95% ee)。从单晶衍射分析中观察到,2,2'-联吡啶-α,α'-CF 3 -二醇配体的络合产生了不寻常的六配位Zn II。