Enantioselective Protonation of Enol Esters with Bifunctional Phosphonium/Thiourea Catalysts
作者:Eiji Yamamoto、Kodai Wakafuji、Yusuke Mori、Gaku Teshima、Yuki Hidani、Makoto Tokunaga
DOI:10.1021/acs.orglett.9b01216
日期:2019.6.7
Bifunctional phosphonium/thioureas derived from tert-leucine behaved as highly selective catalysts for enantioselective protonation of enol esters, providing α-chiral ketones in yields of up to 99% with high enantioselectivities (up to 98.5:1.5 er). Control experiments clarified that a bulky tert-butyl group and phosphonium and thiourea moieties were necessary to achieve such high stereoselectivity
衍生自叔亮氨酸的双官能phospho /硫脲可作为烯醇酯对映选择性质子化的高选择性催化剂,以高对映选择性(高达98.5:1.5 er)提供α-手性酮,收率高达99%。对照实验表明,大的叔丁基基团以及phospho和硫脲部分对于实现如此高的立体选择性是必需的。此外,机理研究表明,该催化剂已转化为相应的甜菜碱,可作为单分子催化剂。