Synthesis of novel chiral bidentatephosphite ligands derived from the pyranoside backbone of monosaccharides and their application in the Cu-catalyzed conjugate addition of dialkylzinc to enones
作者:Qing-Lu Zhao、Lai-Lai Wang
DOI:10.1016/j.tetasy.2011.11.003
日期:2011.11
bidentatephosphite ligands, derived from methyl 3,6-anhydro-α-d-glucopyranoside and chlorophosphoric acid diaryl ester, were easily synthesized. These ligands were successfully employed in the Cu-catalyzed asymmetric conjugate 1,4-addition of the organozinc reagents diethylzinc and/or dimethylzinc to enones. The stereochemically matched combination of glucopyranoside and (R)-H8-binaphthyl in ligand 2,4-bis[(R)-1
容易地合成了由3,6-脱水-α-d-吡喃葡萄糖甲基和氯代磷酸二芳基酯衍生的一系列新的二齿亚磷酸酯配体。这些配体已成功用于有机锌试剂二乙基锌和/或二甲基锌与烯酮的Cu催化的不对称共轭1,4-加成反应。配体2,4-双[(R)-1,1'-H 8-联萘-2,2'-二基]亚磷酸酯}-甲基3中吡喃葡萄糖苷和(R)-H 8-联萘的立体化学匹配组合使用Cu(OTf)2时,在THF中以(S)构型生成3-乙基环己酮的85%ee时,, 6-脱水-α-d-吡喃葡萄糖苷是必不可少的作为催化前体。当反应在从-10℃改变到-80℃的较低温度下进行时,观察到温度对反应的对映选择性的边际影响。在吡喃葡萄糖苷骨架的1位上甲基取代基的存在对ZnEt 2与无环烯酮的1,4-加成中的对映选择性具有负面影响。