31121-43-4Relevant academic research and scientific papers
Implementing Hydrogen Atom Transfer (HAT) Catalysis for Rapid and Selective Reductive Photoredox Transformations in Continuous Flow
Steiner, Alexander,Williams, Jason D.,Rincón, Juan A,de Frutos, Oscar,Mateos, Carlos,Kappe, C. Oliver
, p. 5807 - 5811 (2019)
The reductive transformation of aryl halides and carbonyl compounds is a key step in many photoredox transformations. By combining a highly reducing organic photocatalyst with a thiol hydrogen atom transfer (HAT) catalyst, we showcase rapid and highly selective reactions of these synthetically important starting materials in continuous flow. The fast reduction of aryl iodides, bromides and chlorides has been demonstrated with residence times in some cases below one minute. Selectivity between mono- and di-dehalogenation could also be achieved in some cases. Aryl ketones, aldehydes and imines were shown to undergo facile pinacol couplings, and the coupling of an aryl chloride with a styrene was also successful.
Experimental study of the mechanism of the palladium-catalyzed aryl-alkyl negishi coupling using hybrid phosphine-electron-withdrawing olefin ligands
Gioria, Estefana,Martnez-Ilarduya, Jess M.,Espinet, Pablo
, p. 4394 - 4400 (2014)
A detailed study of the Negishi cross-coupling reaction of ArI (Ar = 2-C6H4CO2Et) and ZnEt2 with palladium catalysts containing conventional phosphines versus one using a chelating hybrid phosphine-electron-withdrawing olefin (P-EWO) ligand reveals that for conventional phosphines (e.g., PPh3) β-H elimination from intermediate [PdArEt(PPh3)2] is competitive with Ar-Et reductive elimination and is responsible for part of the undesired reduction product ArH. In contrast, with the EWO phosphine, the β-H elimination from intermediate [PdArEt(P-EWO)] is slow compared to the fast Ar-Et reductive elimination, and the undesired reduction product ArH observed proceeds in this case of hydrolysis of ZnArEt, formed in transmetalations where Ar is transferred from Pd to Zn. The rate of these transmetalations is comparable to the rate of reductive eliminations. Consequently, undesired transmetalations affording [PdEt2(P-EWO)] and ZnArEt are more effective at early stages of the reactions and less effective when the ethylating agent becomes poorer in ZnEt2 and richer in ZnEtX (X = I), as the reaction proceeds. Careful analysis of the experiments reveals the detailed changing evolution of the reaction, not only providing the main features of the catalytic cycle but also deducing how the reagents in the system change with time and what the effects on the products of these changes are.
A visible-light-photocatalytic water-splitting strategy for sustainable hydrogenation/deuteration of aryl chlorides
Ling, Xiang,Xu, Yangsen,Wu, Shaoping,Liu, Mofan,Yang, Peng,Qiu, Chuntian,Zhang, Guoqiang,Zhou, Hongwei,Su, Chenliang
, p. 386 - 392 (2020/02/25)
Hydrogenation/deuteration of carbon chloride (C?Cl) bonds is of high significance but remains a remarkable challenge in synthetic chemistry, especially using safe and inexpensive hydrogen donors. In this article, a visible-light-photocatalytic watersplitting hydrogenation technology (WSHT) is proposed to in-situ generate active H-species (i.e., Had) for controllable hydrogenation of aryl chlorides instead of using flammable H2. When applying heavy water-splitting systems, we could selectively install deuterium at the C?Cl position of aryl chlorides under mild conditions for the sustainable synthesis of high-valued added deuterated chemicals. Sub-micrometer Pd nanosheets (Pd NSs) decorated crystallined polymeric carbon nitrides (CPCN) is developed as the bifunctional photocatalyst, whereas Pd NSs not only serve as a cocatalyst of CPCN to generate and stabilize H (D)-species but also play a significant role in the sequential activation and hydrogenation/deuteration of C?Cl bonds. This article highlights a photocatalytic-WSHT for controllable hydrogenation/deuteration of low-cost aryl chlorides, providing a promising way for the photosynthesis of high-valued added chemicals instead of the hydrogen evolution.
Deuterium exchange mediated by an iridium-phosphine complex formed in situ
Ellames, George J,Gibson, Jennifer S,Herbert, John M,Kerr, William J,McNeill, Alan H
, p. 6413 - 6416 (2007/10/03)
Bis(triorganophosphine)(cyclooctadiene)iridium(I) tetrafluoroborates, 2, are readily generated in situ and utilised for the exchange of deuterium into a variety of aromatic substrates. The efficiencies of deuterium exchange using 2 formed in this way are comparable to those observed in exchange processes where the isolated pre-catalysts were used.
