78-82-0Relevant articles and documents
Roles of Iron Complexes in Catalytic Radical Alkene Cross-Coupling: A Computational and Mechanistic Study
Kim, Dongyoung,Rahaman, S. M. Wahidur,Mercado, Brandon Q.,Poli, Rinaldo,Holland, Patrick L.
, p. 7473 - 7485 (2019)
A growing and useful class of alkene coupling reactions involve hydrogen atom transfer (HAT) from a metal-hydride species to an alkene to form a free radical, which is responsible for subsequent bond formation. Here, we use a combination of experimental and computational investigations to map out the mechanistic details of iron-catalyzed reductive alkene cross-coupling, an important representative of the HAT alkene reactions. We are able to explain several observations that were previously mysterious. First, the rate-limiting step in the catalytic cycle is the formation of the reactive Fe-H intermediate, elucidating the importance of the choice of reductant. Second, the success of the catalytic system is attributable to the exceptionally weak (17 kcal/mol) Fe-H bond, which performs irreversible HAT to alkenes in contrast to previous studies on isolable hydride complexes where this addition was reversible. Third, the organic radical intermediates can reversibly form organometallic species, which helps to protect the free radicals from side reactions. Fourth, the previously accepted quenching of the postcoupling radical through stepwise electron transfer/proton transfer is not as favorable as alternative mechanisms. We find that there are two feasible pathways. One uses concerted proton-coupled electron transfer (PCET) from an iron(II) ethanol complex, which is facilitated because the O-H bond dissociation free energy is lowered by 30 kcal/mol upon metal binding. In an alternative pathway, an O-bound enolate-iron(III) complex undergoes proton shuttling from an iron-bound alcohol. These kinetic, spectroscopic, and computational studies identify key organometallic species and PCET steps that control selectivity and reactivity in metal-catalyzed HAT alkene coupling, and create a firm basis for elucidation of mechanisms in the growing class of HAT alkene cross-coupling reactions.
NHC-catalyzed silylative dehydration of primary amides to nitriles at room temperature
Ahmed, Jasimuddin,Hota, Pradip Kumar,Maji, Subir,Mandal, Swadhin K.,Rajendran, N. M.
supporting information, p. 575 - 578 (2020/01/29)
Herein we report an abnormal N-heterocyclic carbene catalyzed dehydration of primary amides in the presence of a silane. This process bypasses the energy demanding 1,2-siloxane elimination step usually required for metal/silane catalyzed reactions. A detailed mechanistic cycle of this process has been proposed based on experimental evidence along with computational study.
Synthesis of difluoromethylselenoesters from aldehydes: Via a radical process
Guo, Rui-Li,Zhu, Xue-Qing,Zhang, Xing-Long,Wang, Yong-Qiang
supporting information, p. 8976 - 8979 (2020/08/17)
Difluoromethylselenoester compounds, another important kind of organoselenium compounds, are reported herein for the first time. They can be efficiently synthesized from aldehydes and BnSeCF2H. The synthetic method features mild reaction conditions, broad substrate scope, good tolerance of functional groups, and importantly, no metal is involved in the reaction.
Method for continuous preparation of nitriles in a pipelined reactor (by machine translation)
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Paragraph 0036-0047; 0056; 0058, (2020/12/14)
The method comprises the following steps that a tin catalyst is coated on the inner wall of the pipeline reactor; and the method comprises the following steps: coating a tin catalyst on the inner wall of the pipeline reactor. The amide solution and the catalytic auxiliary agent are mixed and then sent to a pipeline reactor, and the amide is dehydrated to generate nitrile at the reaction pressure of 0.1 - 2.0 mpa and 100 - 200 °C reaction temperature. The resulting reaction product was separated to give the crude product of the nitrile to which the amide corresponded. In the pipeline reactor, the corresponding nitrile is continuously prepared under the action of the tin catalyst, a dehydrating agent is not needed, byproducts only are water, and three wastes are reduced. (by machine translation)
