The synthesis of chiral 3-hydroxy-2-methylpropanoic acid esters (e.g., “Roche ester” 3a) based on the rhodium-catalyzed stereoselective hydrogenation of Baylis–Hillman reaction products was investigated. Full conversions and enantioselectivities of up to 99% at a substrate/catalyst ratio of up to 500/1 were achieved by application of bisphospholanes of the catASium M series as ancillary ligands. An
研究了基于铑催化的Baylis-Hillman反应产物的立体选择性加氢合成手性3-羟基-2-甲基丙酸酯(例如“ Roche酯” 3a)。通过将cat AS ium M系列的双膦酸酯用作辅助配体,可以在高达500/1的底物/催化剂比率下实现高达99%的完全转化率和对映选择性。通过相关的外消旋β-支化前体的非对映选择性羟基定向氢化观察到了有趣的动力学拆分,所述外消旋β-支化前体主要提供具有高达96%ee的抗异构体。
Asymmetric Reductive Aldol-Type Reaction with Carbonyl Compounds Using Dialkyl Tartrate as a Chiral Ligand
An asymmetric reductive aldol-type reaction of α,β-unsaturated esters with carbonyl compounds using Rh catalyst and Et2Zn was investigated. A chiral zinc complex from α,β-unsaturated ester was easily generated as the key intermediate from Et2Zn and Wilkinson's catalyst with diisopropyl L-(+)-tartrate to give a variety of enantioenriched β-hydroxy esters. The reaction was also applied to the intramolecular