Influence of an .alpha.-cyano function on charge delocalization in the benzyl cation. Relationship between inductive destabilization and conjugative stabilization by the cyano group
catalysis promises high catalytic efficiency in the enantioselectivecyanosilylation of ketones through the combined use of a Lewis acid and a Lewis base. Catalyst systems composed of a chiral salen-Al complex and an N-oxide have high catalytic turnovers (200 for aromatic ketones, 1000 for aliphatic ones). With these catalysts, a wide range of aliphatic and aromatic ketones were converted under mild
Synthesis, Characterization, and Reactivity of Lanthanide Amides Incorporating Neutral Pyrrole Ligand. Isolation and Characterization of Active Catalyst for Cyanosilylation of Ketones
作者:Fenhua Wang、Yun Wei、Shaowu Wang、Xiancui Zhu、Shuangliu Zhou、Gaosheng Yang、Xiaoxia Gu、Guangchao Zhang、Xiaolong Mu
DOI:10.1021/om500924q
日期:2015.1.12
3 with Me3SiCN, complexes 2, 3, 4, 5, 7, and 8 as catalysts for cyanosilylation of ketones were investigated. Results indicated that these complexes displayed a high catalytic activity on addition of Me3SiCN to ketones, and the activity of the complexes has the order of 7 ∼ 8 > 2 ∼ 3 ∼ 4 ∼ 5. Thus, complex 7 or 8 was proposed as the activecatalyst in the catalytic reaction for the precatalysts of
Phenolic<i>N</i>-Oxide as a Highly Efficient Organocatalyst for Cyanosilylation of Ketones
作者:Xiaoming Feng、Yan Li、Bin He、Guolin Zhang
DOI:10.1055/s-2004-829072
日期:——
The use of an inexpensive, easy to handle and readily available chemical, 5 mol% phenolic N-oxide, alone as a catalyst for cyanosilylation of ketones gave the corresponding products in 78-99% yield with reaction times of 0.5-16 hours.
A new bifunctional catalytic system based on chiral N-oxide titanium complexes has been used for the asymmetric cyano-silylation of ketones. Screening of a variety of chiral N-oxide metal complexes resulted in (1R,2S)-1-(2'-pyridylmethyl)-2-(diphenylhydroxymethyl)pyrrolidine N-oxide titanium complex, which gave O-TMS cyanohydrins in good yields with enantiomeric excesses of up to 69%. A catalytic cycle
undertaken. When Lewis acid catalysis is dominant, a significantly positive reaction constant is observed, whereas reactions dominated by Lewisbasecatalysis give much smaller reaction constants. [Ti(salen)O}2] was found to show the highest degree of Lewis acid catalysis, whereas two [VO(salen)X] (X=EtOSO3 or NCS) complexes both displayed lower degrees of Lewis acid catalysis. In the case of reactions