Ag
<sup>I</sup>
‐Catalyzed Reaction of Enol Diazoacetates and Imino Ethers: Synthesis of Highly Functionalized Pyrroles
作者:Kuiyong Dong、Ahmad Humeidi、Wendell Griffith、Hadi Arman、Xinfang Xu、Michael P. Doyle
DOI:10.1002/anie.202101641
日期:2021.6.7
AgI-catalyzed efficient method for the coupling of imino ethers and enol diazoacetates through a [3+2]-cycloaddition/C−O bond cleavage/[1,5]-proton transfer cascade process is reported. The general class of imino ethers that includes oxazolines, benzoxazoles and benzimidates are applicable substrates for these reactions that provide direct access to fully substituted pyrroles with uniformly high chemo- and
报道了一种前所未有的 Ag I催化有效方法,用于通过 [3+2]-环加成/C-O 键裂解/[1,5]-质子转移级联过程偶联亚氨基醚和烯醇重氮乙酸酯。包括恶唑啉、苯并恶唑和苯甲亚胺酯在内的一般亚氨基醚类是这些反应的适用底物,可直接获得具有均匀高化学和区域选择性的完全取代的吡咯。吡咯 2-、5- 和 N-位取代的高度可变性表征了这种方法,该方法也提供了通过对所得 N-官能吡咯的轻松修饰来进一步实现吡咯多样化的切入点。
Radical-carbanion cyclo-coupling in armed aromatics: overriding steric hindrance to ring closure
作者:Mark D. Roydhouse、John C. Walton
DOI:10.1039/b506391d
日期:——
Omega-(2-Halophenyl)alkyl-2-oxazolines were prepared and reacted via base promoted intramolecular coupling of radical with carbanionic centres to yield 1-phenyl-1-oxazolino-indan and -tetralin derivatives containing quaternary C-atoms.
Mechanism of SeO2 promoted oxidative rearrangement of 2-substituted oxazolines to dihydrooxazinones: Isotopic labeling and kinetic studies
作者:Cynthia M. Shafer、Daniel I. Morse、Tadeusz F. Molinski
DOI:10.1016/0040-4020(96)00902-7
日期:1996.11
recently reported1 SeO2 promoted oxidative rearrangement of 2-alkyl oxazolines was investigated. 13C labeling studies with showed that rearrangement proceeds by fission and migration of the CN bond, not the CC bond as first proposed. Oxidation-rearrangement of 1 proceeds by rapid SeO2 promoted oxidation to 2-acyloxazoline 3 followed by slower rearrangement of 3 to oxazinone 2. The second order rate
研究了最近报道的1 SeO 2促进2-烷基恶唑啉氧化重排的机理。13 C标记研究表明,重排是通过CN键的裂变和迁移进行的,而不是最初提出的CC键。的氧化重排1个通过快速前进的SeO 2促进氧化成2- acyloxazoline 3随后的重排较慢3至恶嗪酮2。在40°C下1,4-二恶烷中2,4-二苯基恶唑啉1b氧化步骤的二级速率常数为k 1 = 2.85±0.62×10-2 M -1 ·s -1。限速重排的第二步的一级速率常数为k 2 = 1.15±0.09×10 -3 s -1,而在存在下限的情况下,活化能E A的相对较低的表观能量为4.2±1.6 kcal·mol -1。 SeO 2的当量浓度为2.0当量,表明存在多相催化作用。该反应由路易斯酸(包括SeO 2或少量H 2 O)催化。提出了一种合理的机理,涉及路易斯酸活化和H 2 O的亲核催化。
Oxidative Rearrangement of 2-Substituted Oxazolines. A Novel Entry to 5,6-Dihydro-2<i>H</i>-1,4-oxazin-2-ones and Morpholin-2-ones
作者:Cynthia M. Shafer、Tadeusz F. Molinski
DOI:10.1021/jo952144f
日期:1996.1.1
A novel synthesis of 5,6-dihydro-2H-1,4-oxazin-2-ones by SeO2-promoted oxidative rearrangement of 2-alkyl- and 2-(arylmethyl)oxazolines is described. Yields are good to excellent; (up to 94%) with the highest yields obtained for 2-arylmethyl- and 2-neopentyl-substituted oxazolines. This reaction provides convenient access to novel 5-aryl-substituted dihydrooxazinones in high yield. The latter compounds are important ''chiral glycine'' synthons for asymmetric synthesis of a-amino acids. Since oxazolines are readily derived from carboxylic acids or their equivalents, this oxidative rearrangement constitutes an entry to synthesis of a-amino acids from carboxylic acids. A mechanism is proposed to account for the rearrangement involving a ''nitrilium to acylium'' 1,2-migration.
Benzyne-mediated trichloromethylation of chiral oxazolines
A three-component reaction between benzyne, oxazolines and chloroform was developed for the synthesis of trichloromethylated chiral oxazolidines. Benzyne not only serves as an electrophile towards oxazolines but also acts as a base for the deprotonation of chloroform. The dual functions of benzyne enable the trichloromethylation of chiral oxazolines and thus construct chiral N,O-quaternary stereocenters