Novel tetradentate bisoxazoline ligands from l-serine and β-DDB for asymmetric pinacol coupling reactions of aromatic aldehydes
作者:Jiwu Wen、Limin Liu、Xiaochun Zhou、Ronghua Hu、Yaping Xu
DOI:10.1016/j.tetasy.2013.05.026
日期:2013.7
A variety of novel hydroxyl-containing tetradentate bisoxazolines were successfully synthesized from natural l-serine and β-DDB. The applications of these ligands in the asymmetric pinacol coupling of aromatic aldehydes revealed that the absolute configurations of the resulting pinacols were entirely dominated by the axial chirality of the biphenyl component and that the bulky substituent adjacent
从天然的l-丝氨酸和β-DDB成功地合成了多种新颖的含羟基的四齿双恶唑啉。这些配体在芳族醛的不对称频哪醇偶联中的应用表明,所得频哪醇的绝对构型完全由联苯组分的轴向手性支配,与羟基相邻的庞大取代基有利于实现高非对映选择性和对映选择性。在所筛选的配体中,(S,a R,S)-1c表现出更好的不对称诱导能力以提供(R,R)对映异构体,非对映选择性高达99/1,对映体过量63-89%。还提出了不对称频哪醇偶联的合理机制。