scholarly journals A combination of experimental and computational methods to study the reactions during a Lignin-First approach

2020 ◽  
Vol 92 (4) ◽  
pp. 631-639
Author(s):  
Ivan Kumaniaev ◽  
Elena Subbotina ◽  
Maxim V. Galkin ◽  
Pemikar Srifa ◽  
Susanna Monti ◽  
...  
Keyword(s):  
Transition Metal ◽  
Hydrogen Transfer ◽  
Transfer Hydrogenation ◽  
Metal Catalyst ◽  
Main Role ◽  
One Pot ◽  
Transition Metal Catalyst ◽  
Transition Metal Catalyzed ◽  
Catalyzed Reactions ◽  
Metal Catalyzed

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.

Advances in Transition-Metal-Catalyzed C–H Bond Oxygenation of Amides

Synthesis ◽  
2021 ◽  
Author(s):  
Muniyappa Vijaykumar ◽  
Benudhar Punji
Keyword(s):  
Transition Metal ◽  
Organic Synthesis ◽  
Bond Formation ◽  
Metal Catalyst ◽  
Transition Metal Catalyst ◽  
Amide Derivatives ◽  
Directing Group ◽  
Transition Metal Catalyzed ◽  
Metal Catalyzed ◽  
Tertiary Amides

The C–O bond formation represents a fundamental chemical transformation in organic synthesis to develop valuably oxygenated (hetero)arenes. Particularly, the direct and regioselective C–H bond oxygenation of privileged amides, using a transition metal catalyst and a mild oxygenating source, is a step-economy and attractive approach. During the last decade, considerable progress has been realized in the direct C−H oxygenation of primary, secondary and tertiary amides. This Minireview compiles the advances in transition-metal-catalyzed oxygenation of C(sp<sup>2</sup>)−H and C(sp<sup>3</sup>)−H bonds on various amides with diverse oxygenation sources. The review is categorized into two different major sections: (i) C(sp<sup>2</sup>)−H oxygenation and (ii) C(sp<sup>3</sup>)−H oxygenation. Each section is discussed based on the directing group (monodentate and bidentate) attached to the amide derivatives.

Monodentate Trialkylphosphines: Privileged Ligands in Metal-catalyzed Crosscoupling Reactions

2020 ◽  
Vol 24 (3) ◽  
pp. 231-264 ◽  
Author(s):  
Kevin H. Shaughnessy
Keyword(s):  
Transition Metal ◽  
Cross Coupling ◽  
Coupling Reactions ◽  
Cross Coupling Reactions ◽  
Aryl Bromides ◽  
Wide Range ◽  
Sterically Demanding ◽  
Transition Metal Catalyzed ◽  
Catalyzed Reactions ◽  
Metal Catalyzed

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.

Chemistry of Unsymmetrical C1-Substituted Oxabenzonorbornadienes

2021 ◽  
Vol 17 ◽  
Author(s):  
Austin Pounder ◽  
Angel Ho ◽  
Matthew Macleod ◽  
William Tam
Keyword(s):  
Transition Metal ◽  
Metal Complexes ◽  
Transition Metal Complexes ◽  
Substituent Effects ◽  
Face Selectivity ◽  
Transition Metal Catalyzed ◽  
Catalyzed Reactions ◽  
Metal Catalyzed ◽  
Synthetic Intermediate

: Oxabenzonorbornadiene (OBD) is a useful synthetic intermediate which can be readily activated by transition metal complexes with great face selectivity due to its dual-faced nature and intrinsic angle strain on the alkene. To date, the understanding of transition-metal catalyzed reactions of OBD itself has burgeoned; however, this has not been the case for unsymmetrical OBDs. Throughout the development of these reactions, the nature of C1-substituent has proven to have a profound effect on both the reactivity and selectivity of the outcome of the reaction. Upon substitution, different modes of reactivity arise, contributing to the possibility of multiple stereo-, regio-, and in extreme cases, constitutional isomers which can provide unique means of constructing a variety of synthetically useful cyclic frameworks. To maximize selectivity, an understanding of bridgehead substituent effects is crucial. To that end, this review outlines hitherto reported examples of bridgehead substituent effects on the chemistry of unsymmetrical C1-substituted OBDs.

scholarly journals Transition metal-catalyzed reactions of N-sulfinyl imines

2021 ◽  
pp. 153104
Author(s):  
Francisco Foubelo ◽  
Carmen Nájera ◽  
José M. Sansano ◽  
Miguel Yus
Keyword(s):  
Transition Metal ◽  
Transition Metal Catalyzed ◽  
Catalyzed Reactions ◽  
Metal Catalyzed

Iodide effects in transition metal catalyzed reactions

2004 ◽  
pp. 3409 ◽  
Author(s):  
Peter M. Maitlis ◽  
Anthony Haynes ◽  
Brian R. James ◽  
Marta Catellani ◽  
Gian Paolo Chiusoli
Keyword(s):  
Transition Metal ◽  
Transition Metal Catalyzed ◽  
Catalyzed Reactions ◽  
Metal Catalyzed

Transition-Metal-Catalyzed Reactions Involving Arynes

Synthesis ◽  
2017 ◽  
Vol 50 (01) ◽  
pp. 1-16 ◽  
Author(s):  
Santosh Mhaske ◽  
Ranjeet Dhokale
Keyword(s):  
Natural Products ◽  
Transition Metal ◽  
Total Synthesis ◽  
Scientific Community ◽  
Multicomponent Reactions ◽  
Polycyclic Aromatic Compounds ◽  
Polycyclic Aromatic ◽  
Transition Metal Catalyzed ◽  
Catalyzed Reactions ◽  
Metal Catalyzed

The plethora of transformations attainable by the transition-metal-catalyzed reactions of arynes has found immense contemporary interest in the scientific community. This review highlights the scope and importance of transition-metal-catalyzed aryne reactions in the field of synthetic organic chemistry reported to date. It covers transformations achieved by the combination of arynes and various transition metals, which provide a facile access to a biaryl motif, fused polycyclic aromatic compounds, different novel carbocycles, various heterocycles, and complex natural products.1 Introduction2 Insertion of Arynes3 Annulation of Arynes4 Cycloaddition of Arynes5 Multicomponent Reactions of Arynes6 Miscellaneous Reactions of Arynes7 Total Synthesis of Natural Products Using Arynes8 Conclusion

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