Asymmetric [3 + 2] Cycloaddition of Chiral <i>N</i>-Phosphonyl Imines with Methyl Isocyanoacetate for Accessing 2-Imidazolines with Switchable Stereoselectivity
作者:Shuo Qiao、Cody B. Wilcox、Daniel K. Unruh、Bo Jiang、Guigen Li
DOI:10.1021/acs.joc.6b03068
日期:2017.3.17
Asymmetric [3 + 2] cycloaddition of chiral N-phosphonyl imines with methyl isocyanoacetate has been established, enabling controllable/switchable stereoselectivity access to 21 examples of cycloadducts with good to excellent chemical yields (up to 92%) and high diastereoselectivities (up to 99:1 dr). The cycloadditionreaction promoted by Cs2CO3 resulted in diastereoenriched (4R,5S)-products with >99:1
Chiral N-phosphonyl imine chemistry: Asymmetric synthesis of α,β-diamino esters by reacting phosphonyl imines with glycine enolates
作者:Teng Ai、Guigen Li
DOI:10.1016/j.bmcl.2009.03.001
日期:2009.7
Chiral phosphonyl imines attached with N-isopropyl protection group were found to react with lithium glycine enolates under convenient conditions to give alpha,beta-diamino esters. Thirteen examples have been examined in good to excellent chemical yields (85-97%) diastereoselectivity (up to 99% de). By treating with HBr at room temperature, the chiral auxiliary can be readily removed and recycled. The absolute structure has been unambiguously determined by converting a product to a known sample. Published by Elsevier Ltd.