根据三氟乙酸在70°下测得的某些环烷基和仲烷基苯(RPh)的电去铁酸酯化速率,可以确定邻位和对位取代的部分速率因子如下:(R =)环丁基,455 ,1,070;环戊基473,1 195:环己基406,886:1-甲基乙基,223,544; 1-甲基丙基,244,690:1-乙基丙基,196,682:1-乙基丁基,217,685。除后两种化合物外,每个烷基苯给出的常数log f o:log f p氢交换中大量其他芳香族化合物的比率为0.865±0.025;该比率是由Wheland中间体中的电荷分布精确预测的。这种相关性允许首先分配有意义的σ +邻位取代基常数,以应用于这些化合物的亲电子取代(但不允许其类似的侧链反应)。交易所在邻1-乙基丁基-苯和1-乙基丙基-苯的-位可能会稍微受阻;这些化合物之间的交换还伴随着分子间表面催化的烷基迁移,该迁移可能在空间上加速。讨论了环状取代基相对于其开链类似
New ligands and structural insights into the catalytic asymmetric addition of organozinc reagents to ketones
作者:Gabriela Huelgas、Lynne K. LaRochelle、Lucrecia Rivas、Yekaterina Luchinina、Rubén A. Toscano、Patrick J. Carroll、Patrick J. Walsh、Cecilia Anaya de Parrodi
DOI:10.1016/j.tet.2011.04.022
日期:2011.6
considerable attention. Outlined herein is the synthesis of two new ligandsbased on the C2-symmetric 11,12-diamino-9,10-dihydro-9,10-ethanoanthracene. The scope of the new ligands has been evaluated in the catalytic asymmetric addition of diethylzinc to a variety of ketones. Enantioselectivities as high as 99% have been achieved. The structures of two of these ligands have been determined by X-ray crystallography
Synergistic Relay Reactions To Achieve Redox‐Neutral α‐Alkylations of Olefinic Alcohols with Ruthenium(II) Catalysis
作者:Chen‐Chen Li、Jian Kan、Zihang Qiu、Jianbin Li、Leiyang Lv、Chao‐Jun Li
DOI:10.1002/anie.201915218
日期:2020.3.9
the first Grignard-type nucleophilic addition using olefinicalcohols as latent carbonyl groups, providing a higher yield of the corresponding secondary alcohol than the classical hydrazone addition to aldehydes does. A broad scope of unsaturated alcohols and hydrazones, including some complex structures, can be successfully employed in this reaction, which shows the versatility of this approach and
Cleavage Reactions of Alkoxy Radicals Produced by Anodic Oxidation of<i>t</i>-Alcohols
作者:Kazuhiro Maruyama、Katsuya Murakami
DOI:10.1246/bcsj.41.1401
日期:1968.6
oxidation of t-alcohols in water - dioxane - sodium hydroxide system has been examined. The possibility of production of t-alkoxy radicals by anodic oxidation of t-alcohols in the electrolytic system was found. The relative ease of bond scission of the intermediate t-alkoxy radical was determined by quantitative analysis of the mixture of ketones produced. The relativerates of cleavage decrease in the order:
13C NMR spectroscopic comparison of sterically stabilized meta- and para-substituted o-tolyldi(adamant-1-yl)methyl cations with conjugatively stabilized benzyl cations
作者:John S. Lomas
DOI:10.1039/p29960002601
日期:——
series of meta- and para-substituted anti-o-tolyldi(adamant-1-yl)methyl cations has been generated by reaction of anti-o-tolyldi(adamant-1-yl)methanols with trifluoroacetic acid in chloroform. 13C NMR spectroscopy indicates small but significant variations in the chemical shifts of the charged carbon and its nearest neighbours on the adamantyl groups, and departures from additivity of substituent effects
Additions of Organomagnesium Halides to α-Alkoxy Ketones: Revision of the Chelation-Control Model
作者:Jacquelyne A. Read、Yingying Yang、K. A. Woerpel
DOI:10.1021/acs.orglett.7b01161
日期:2017.7.7
obtained in additions of organometallic nucleophiles to α-alkoxy ketones but fails for reactions of allylmagnesium halides. Low diastereoselectivity in ethereal solvents results from no chelation-induced rate acceleration. Additions of allylmagnesium bromide to carbonyl compounds are diastereoselective using CH2Cl2 as the solvent even though rate acceleration is still absent. Stereoselectivity likely arises