Transition-Metal-Catalyzed Reduction: Hydrogenation and Transfer ­Hydrogenation

Author(s):  
L. R. Cox
2020 ◽  
Vol 92 (4) ◽  
pp. 631-639
Author(s):  
Ivan Kumaniaev ◽  
Elena Subbotina ◽  
Maxim V. Galkin ◽  
Pemikar Srifa ◽  
Susanna Monti ◽  
...  

AbstractCurrent pulping technologies only valorize the cellulosic fiber giving total yields from biomass below 50 %. Catalytic fractionation enables valorization of both cellulose, lignin, and, optionally, also the hemicellulose. The process consists of two operations occurring in one pot: (1) solvolysis to separate lignin and hemicellulose from cellulose, and (2) transition metal catalyzed reactions to depolymerize lignin and to stabilized monophenolic products. In this article, new insights into the roles of the solvolysis step as well as the operation of the transition metal catalyst are given. By separating the solvolysis and transition metal catalyzed hydrogen transfer reactions in space and time by applying a flow-through set-up, we have been able to study the solvolysis and transition metal catalyzed reactions separately. Interestingly, the solvolysis generates a high amount of monophenolic compounds by pealing off the end groups from the lignin polymer and the main role of the transition metal catalyst is to stabilize these monomers by transfer hydrogenation/hydrogenolysis reactions. The experimental data from the transition metal catalyzed transfer hydrogenation/hydrogenolysis reactions was supported by molecular dynamics simulations using ReaXFF.


2020 ◽  
Vol 7 (8) ◽  
pp. 1022-1060 ◽  
Author(s):  
Wenbo Ma ◽  
Nikolaos Kaplaneris ◽  
Xinyue Fang ◽  
Linghui Gu ◽  
Ruhuai Mei ◽  
...  

This review summarizes recent advances in C–S and C–Se formations via transition metal-catalyzed C–H functionalization utilizing directing groups to control the site-selectivity.


2020 ◽  
Vol 24 (3) ◽  
pp. 231-264 ◽  
Author(s):  
Kevin H. Shaughnessy

Phosphines are widely used ligands in transition metal-catalyzed reactions. Arylphosphines, such as triphenylphosphine, were among the first phosphines to show broad utility in catalysis. Beginning in the late 1990s, sterically demanding and electronrich trialkylphosphines began to receive attention as supporting ligands. These ligands were found to be particularly effective at promoting oxidative addition in cross-coupling of aryl halides. With electron-rich, sterically demanding ligands, such as tri-tertbutylphosphine, coupling of aryl bromides could be achieved at room temperature. More importantly, the less reactive, but more broadly available, aryl chlorides became accessible substrates. Tri-tert-butylphosphine has become a privileged ligand that has found application in a wide range of late transition-metal catalyzed coupling reactions. This success has led to the use of numerous monodentate trialkylphosphines in cross-coupling reactions. This review will discuss the general properties and features of monodentate trialkylphosphines and their application in cross-coupling reactions of C–X and C–H bonds.


2015 ◽  
Vol 20 (5) ◽  
pp. 471-511 ◽  
Author(s):  
Satyasheel Sharma ◽  
Neeraj Kumar Mishra ◽  
Youngmi Shin ◽  
In Su Kim

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