Seifert Cole W, Pindi Suresh, Li Guigen
†Department of Chemistry and Biochemistry, Texas Tech University, Lubbock, Texas 79409-1061, United States.
J Org Chem. 2015 Jan 2;80(1):447-52. doi: 10.1021/jo5024443. Epub 2014 Dec 9.
Carbamoyl anions were found to smoothly react with chiral N-phosphonyl imines in toluene at -78 °C to r.t. using LiHMDS as the base. Group-assisted purification (GAP) has been utilized to give the pure amides without using column chromatography or recrystallization. The asymmetric reaction resulted in chiral N-phosphonyl amino amides with good to excellent yields (71-99%) and good crude diastereoselectivities (dr 84:16-95:5). In this GAP procedure, the crude solids are washed with diethyl ether to afford the pure products, as revealed by (1)H NMR analysis; GAP washing consistently increases the diastereopurity of the products, resulting in excellent diastereoselectivities, often with final dr > 99:1. Interestingly, the diastereoenriched products can be obtained either in the ether solution or as the suspended solid, depending on the substrate.
发现在-78°C至室温的甲苯中，以LiHMDS作为碱时，氨基甲酰阴离子能与手性N-膦酰基亚胺顺利反应。已利用基团辅助纯化（GAP）在不使用柱色谱或重结晶的情况下得到纯酰胺。该不对称反应生成手性N-膦酰基氨基酰胺，产率良好至优异（71-99%），粗品非对映选择性良好（dr 84:16-95:5）。在该GAP程序中，粗固体用乙醚洗涤以得到纯产物，如通过¹H NMR分析所示；GAP洗涤持续提高产物的非对映纯度，从而产生优异的非对映选择性，最终dr通常>99:1。有趣的是，根据底物的不同，可在乙醚溶液中或作为悬浮固体获得非对映体富集产物。
