1436-44-8Relevant articles and documents
POLAR EFFECTS IN FREE-RADICAL REACTIONS. NEW SYNTHETIC DEVELOPMENTS IN THE FUNCTIONALIZATION OF HETEROAROMATIC BASES BY NUCLEOPHILIC RADICALS
Minisci, Francesco,Citterio, Attilio,Vismara, Elena,Giordano, Claudio
, p. 4157 - 4170 (1985)
The synthetic interest of the direct substitution of protonated heteroaromatic bases by nucleophilic carbon-centered radicals is furtheron developed by the following new achievements: i) utilization of the redox system N(+)H3OH/Ti(III) in several solvents; ii) utilization of benzoyl peroxide in alcohols; iii) carbamoylation by HCONH2 and H2O2 in the presence of catalytic amounts of Fe(II).These systems allow to obtain either substitution till now tried without success or reactions of industrial interest.Polar effects play a dominat role in determining reactivity, selectivity and synthetic applications; in particular the role of the strongly nucleophilic intermediate radicals of pyridinyl type in the rearomatization step is emphasized.
Substrate-Specific Heterogeneous Catalysis of CeO2 by Entropic Effects via Multiple Interactions
Tamura, Masazumi,Sawabe, Kyoichi,Tomishige, Keiichi,Satsuma, Atsushi,Shimizu, Ken-Ichi
, p. 20 - 26 (2015)
Achieving complete substrate specificity through multiple interactions like an enzyme is one of the ultimate goals in catalytic studies. Herein, we demonstrate that multiple interactions between the CeO2 surface and substrates are the origin of substrate-specific hydration of nitriles in water by CeO2, which is exclusively applicable to the nitriles with a heteroatom (N or O) adjacent to the α-carbon of the CN group but is not applicable to the other nitriles. Kinetic studies reveal that CeO2 reduces the entropic barrier (TΔS?) for the reaction of the former reactive substrate, leading to 107-fold rate enhancement compared with the latter substrate. Density functional theory (DFT) calculations confirmed multiple interaction of the reactive substrate with CeO2, as well as preferable approximation and alignment of the nitrile group of the substrate to the active OH group on CeO2 surface. This can lead to the reduction of the entropic barrier. This is the first example of an entropy-driven substrate-specific catalysis of a nonporous metal oxide surface, which will provide a new design strategy for enzyme-inspired synthetic catalysts.
Direct Oxidative Amination of the Methyl C-H Bond in N-Heterocycles over Metal-Free Mesoporous Carbon
Long, Xiangdong,Wang, Jia,Gao, Guang,Nie, Chao,Sun, Peng,Xi, Yongjie,Li, Fuwei
, p. 10902 - 10912 (2021/09/08)
Direct oxidative amination of the sp3C-H bond is an attractive synthesis route to obtain amides. Conventional catalytic systems for this transformation are based on transition metals and complicated synthesis processes. Herein, direct and efficient oxidative amination of the methyl C-H bond in a wide range of N-heterocycles to access the corresponding amides over metal-free porous carbon is successfully developed. To understand the fundamental structure-activity relationships of carbon catalysts, the surface functional groups and the graphitization degree of porous carbon have been purposefully tailored through doping with nitrogen or phosphorus. The results of characterization, kinetic studies, liquid-phase adsorption experiments, and theoretical calculations indicate that the high activity of the carbon catalyst is attributed to the synergistic effect of surface acidic functional groups (hydroxyl/carboxylic acid/phosphate) and more graphene edge structures exposed on the surface of carbon materials with a high graphitization degree, in which the role of acidic functional groups is to adsorb the substrate molecule and the role of the graphene edge structure is to activate O2
Mild and selective heterogeneous catalytic hydration of nitriles to amides by flowing through manganese dioxide
Battilocchio, Claudio,Hawkins, Joel M.,Ley, Steven V.
supporting information, p. 1060 - 1063 (2016/10/17)
A sustainable flow chemistry process for the hydration of nitriles, whereby an aqueous solution of the nitrile is passed through a column containing commercially available amorphous manganese dioxide, has been developed. The product is obtained simply by concentration of the output stream without any other workup steps. The protocol described is rapid, robust, reliable, and scalable, and it has been applied to a broad range of substrates, showing a high level of chemical tolerance.
