Group-Assisted Purification Chemistry for Asymmetric Mannich-type Reaction of Chiral <i>N</i>-Phosphonyl Imines with Azlactones Leading to Syntheses of α-Quaternary α,β-Diamino Acid Derivatives
作者:Haowei Zhang、Zhen Yang、Brian Nlong Zhao、Guigen Li
DOI:10.1021/acs.joc.7b02556
日期:2018.1.19
An asymmetric Mannich-type reaction between chiral N-phosphonyl imines and azlactones [oxazol-5(4H)-ones] has been established under convenient conditions at room temperature. The reaction was performed without using any bases, additives, or catalysts to achieve up to excellent chemical yields and diastereoselectivity for 32 examples. The α-quaternary syn-α,β-diamino acid products were purified simply
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
N,N-Diisopropyl-N-phosphonyl imines lead to efficient asymmetric synthesis of aziridine-2-carboxylic esters
作者:Padmanabha V. Kattamuri、Yiwen Xiong、Yi Pan、Guigen Li
DOI:10.1039/c3ob40251g
日期:——
Highly diastereoselective asymmetric synthesis of chiral aziridine-2-carboxylicesters is reported for 20 examples with good yields (51–87%) and excellent diastereoselectivities (>99 : 1 dr for most cases). The modified N-phosphonyl imines have proven to be superior to previous imine auxiliaries for the aza Darzens reaction by using a secondary isopropyl group to replace the primary benzyl group for
据报道,手性氮丙啶-2-羧酸酯的高度非对映选择性不对称合成有 20 个实例,具有良好的产率(51-87%)和出色的非对映选择性(大多数情况下 >99:1 dr)。通过使用仲异丙基取代N , N的伯苄基,已证明改性N - 膦酰基亚胺在 aza Darzens 反应中优于以前的亚胺助剂。-二氨基保护。同时,发现在 4 Å 分子筛存在的情况下,在该温度下将预冷的亚胺溶液在 -78 °C 下缓慢加入到预先形成的 β-溴化烯醇锂混合物中的特殊操作对产率至关重要和非对映选择性。本方法可以提供对 β-羟基α-氨基酸和其他重要氨基构建块的简单和通用的访问。
Group-assisted Purification (GAP) Chemistry/Technology in Synthesizing the Chiral Intermediate of Rivastigmine and Its <i>α</i>-Alkyl Benzylamine Analogues
Introduction of (S)-configuration is the key step in the synthesis of the anti-dementia drug Rivastigmine. Twenty-one alkylation products were obtained through simple washing with hexane/ethyl acet...
The GAP chemistry for chiral N-phosphonyl imine-based Strecker reaction
作者:Parminder Kaur、Walter Wever、Suresh Pindi、Raizada Milles、Peng Gu、Min Shi、Guigen Li
DOI:10.1039/c1gc15029d
日期:——
Chiral N-phosphonyl imines were found to be efficient electrophiles for reaction with diethylaluminium cyanide, a non-volatile and inexpensive cyanide source. The reaction produced chiral Strecker adducts, α-aminonitriles, in excellent chemical yields (94–98%) and diastereoselectivities (95 : 5 to >99%). This synthesis was confirmed to follow the GAP chemistry (group-assistant-purification chemistry) process, which can avoid traditional chromatography and recrystallization purifications, i.e., the pure chiral α-aminonitriles bearing a chiral N-phosphonyl group can be simply obtained by washing the solid crude products with hexane. The chiral N-phosphonyl auxiliary can be easily cleaved under mildly acidic conditions and quantitatively recycled by a one-time extraction with n-butanol.
研究发现,手性 N-膦酰亚胺是与氰化二乙基铝(一种非挥发性的廉价氰化物来源)反应的高效亲电体。反应生成了手性 Strecker 加合物--α-氨基硝酰胺,化学收率(94-98%)和非对映选择性(95:5->99%)都非常好。经证实,该合成采用了 GAP 化学(基团辅助纯化化学)工艺,可避免传统的色谱法和重结晶纯化,即只需用正己烷洗涤固体粗产物,即可获得带有手性 N-膦酰基的纯手性 α-氨基硝酸酯。手性 N-膦酰基助剂可在弱酸性条件下轻松裂解,并通过正丁醇一次性萃取定量回收。