据报道,高效手性酯烯酸酯-亚胺缩合可产生具有出色的反式-顺式或反式-非对映体选择性的3,4-二取代的β-内酰胺。手性信息包括在缩合的亲电子伙伴中,名义上为手性α-,β-甲硅烷氧基-或烷氧基-N-三甲基甲硅烷基亚胺。高非对映选择性是由反应介质中存在的金属阳离子的正确选择和羟基保护基团的性质决定的。通过这种方法,已经获得了许多氮杂环丁酮类化合物,它们是合成商业上感兴趣的β-内酰胺类抗生素的中间体。报道了如此获得的氮杂环丁酮的完全归属的1 H和13 C NMR谱。
Unusual and Unexpected Reactivity of <i>t-</i>Butyl Dicarbonate (Boc<sub>2</sub>O) with Alcohols in the Presence of Magnesium Perchlorate. A New and General Route to <i>t-</i>Butyl Ethers
[reaction: see text] A new mild method for protecting alcohols as t-butylethers is reported. The reaction proceeds with Mg(ClO4)2 and Boc2O and shows general applicability. The deprotection of t-butylethers has also been revisited. Preliminary results indicate the CeCl3 x 7H2O/NaI system is a very suitable catalyst for their removal.
[反应:见正文]据报道,一种新的温和的保护叔丁醚醇的方法。反应与Mg(ClO4)2和Boc2O进行,显示出一般的适用性。也已经重新考虑了叔丁基醚的脱保护。初步结果表明,CeCl3 x 7H2O / NaI体系是非常适合去除它们的催化剂。
Acyl Radical Addition to Activated Olefins: A Stereocontrolled Route to Polysubstituted Tetrahydrofurans and Lactones, and Application to the Total Synthesis of (+)-No. 2106 A
作者:Simon Grélaud、Jonathan Lusseau、Yannick Landais
DOI:10.1002/ejoc.201601624
日期:2017.3.10
Addition of acyl radicals to Baylis‐Hillman adducts followed by acetalization and reduction with (Me3Si)3SiH provides the corresponding tetrahydrofurans with moderate 1,2‐ but high 1,3‐stereocontrol. Similar addition to methylenelactones was shown to afford tetrahydrofuran–lactones with high stereocontrol, this strategy being then applied to the total synthesis of (+)‐no. 2106 A.
most underused alcohol protectinggroups. After having developed an easy and useful protocol for its introduction, we offer here a simple procedure for its removal by treatment with anhydrous CeCl3 and NaI in CH3CN. The procedure led to the successful cleavage of aliphatic and aromatic tert-butyl ethers and was compatible with various other functionalities and protectinggroups present in the molecule