Conversion of α,β-Unsaturated Aldehydes into Saturated Esters: An Umpolung Reaction Catalyzed by Nucleophilic Carbenes
作者:Audrey Chan、Karl A. Scheidt
DOI:10.1021/ol050100f
日期:2005.3.1
species from alpha,beta-unsaturated aldehydes. These nucleophilic intermediates can be protonated, and the resulting activated carbonyl unit is trapped with an alcohol nucleophile, thereby promoting a highly efficient conversion of an alpha,beta-unsaturated aldehyde into a saturated ester. A kinetic resolution of secondary alcohols can be achieved using chiral imidazoylidene catalysts. [reaction: see text]
A novel N-formylation and related reactions proceed from cyanides promoted by esters.
酯促进的氰化物引发了新的N-甲酰化反应和相关的反应。
Conformational studies of aminomethylene-malonic acid dimethylester and its N-methyl derivatives using vibrational spectroscopy, X-ray analysis and ab initio calculations
N -methyl derivatives (MAMDME and DMAMDME) were measured in solid phase and in different solvents at various temperatures. X-ray analysis revealed that AMDME exists in solid phase as EZ conformer, MAMDME as ZZa conformer and DMAMDME as ZE conformer (the first and second E or Z letters express the orientation of the carbonyl oxygen to the C C double bond for trans and cis methylester group, respectively
摘要 对氨基亚甲基-丙二酸二甲酯(AMDME) [NH 2 CH C(COOCH 3 ) 2 ] 及其N-甲基衍生物(MAMDME 和DMAMDME) 在固相和不同溶剂中在不同温度下的红外光谱和拉曼光谱进行了测量。X 射线分析表明 AMDME 作为 EZ 构象异构体存在于固相中,MAMDME 作为 ZZa 构象异构体和 DMAMDME 作为 ZE 构象异构体(第一个和第二个 E 或 Z 字母表示反式和顺式甲酯的羰基氧对 CC 双键的取向基团,第三个字母 a 表示甲氨基相对于 CC 双键的反位)。在极性较小的溶液中,主要观察到 AMDME 的两种 ZZ 和 EZ 构象形式以及 MAMDME 的 ZZa 和 EZa,而在极性较大的环境中,还出现了第三种构象形式(分别为 ZE 和 ZEa)。DMAMDME 的行为是不同的,因为没有分子内氢键,并且在极性较小的溶液中以两种 ZZ 和 ZE 构象形式
Catalytic, Enantioselective β-Protonation through a Cooperative Activation Strategy
作者:Michael H. Wang、David Barsoum、C. Benjamin Schwamb、Daniel T. Cohen、Brian C. Goess、Matthias Riedrich、Audrey Chan、Brooks E. Maki、Rama K. Mishra、Karl A. Scheidt
DOI:10.1021/acs.joc.7b00334
日期:2017.5.5
only feasible, but also adaptable to a kinetic resolution of secondaryalcohols through NHC-catalyzed acylation. In-depth analysis of this process determined that careful catalyst and solvent pairing is critical for optimal yield and selectivity; proper choice of nonpolar solvent provided improved yield through suppression of an oxidative side reaction, while employment of a cooperative catalytic approach
Synthesis of Nucleosides and Related Compounds. XXVI. The Difference in Efects between High Pressure and LiClO4 for the Diels-Alder Reaction of Cyclopentadiene with Methylenemalonates or O-Acetylisonitrosomalonates.
作者:Nobuya KATAGIRI、Ayumu KURIMOTO、Chikara KANEKO
DOI:10.1248/cpb.40.1737
日期:——
Diels-Alder reactions of cyclopentadiene with methylenemalonates or O-acetylisonitrosomalonates in the presence of LiClO4 as the catalyst were examined and the results were compared with those obtained under high pressure without the catalyst. Diels-Alder reaction of cyclopentadiene with dimethyl acetoxymethylenemalonate (1) in the presence of LiClO4 afforded the [4+2] adduct (2) as a mixture of endo- and exo-isomers, whose ratio was 2.0, irrespective of the solvent or the concentration of LiClO4. Asymmetric Diels-Alder reaction of cyclopentadiene with di-l-methyl acetoxymethylenemalonate (3) was accelerated remarkably by LiClO4. The configurations of both endo and exo adducts corresponded to the natural form (D-form). These results suggested strongly that LiClO4 would behave as a bidentate Lewis acid catalyst just like titanium tetrachloride. the hetero Diels-Alder reaction of cyclopentadiene with O-acetylisonitrosomalonate in LiClO4-ether produced the adduct (5) in a higher yield than the reaction performed under high pressure.