scholarly journals Visible-Light Radical–Radical Coupling vs. Radical Addition: Disentangling a Mechanistic Knot

Catalysts ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 922
Author(s):  
Fernando Aguilar-Galindo ◽  
Ricardo I. Rodríguez ◽  
Leonardo Mollari ◽  
José Alemán ◽  
Sergio Díaz-Tendero
Keyword(s):  
Radical Addition ◽  
Mechanistic Study ◽  
Cascade Process ◽  
Radical Coupling ◽  
Quantum Chemistry Calculations ◽  
Heterocyclic Derivatives ◽  
Selective Generation ◽  
Imine Reduction ◽  
Process Strategy ◽  
Insight Into

A highly enantioselective protocol has been recently described as allowing the synthesis of five-membered cyclic imines harnessing the selective generation of a β-Csp3-centered radical of acyl heterocyclic derivatives and its subsequent interaction with diverse NH-ketimines. The overall transformation represents a novel cascade process strategy crafted by individual well-known steps; however, the construction of the new C-C bond highlights a crucial knot from a mechanistically perspective. We believe that the full understanding of this enigmatic step may enrich the current literature and expand latent future ideas. Therefore, a detailed mechanistic study of the protocol has been conducted. Here, we provide theoretical insight into the mechanism using quantum chemistry calculations. Two possible pathways have been investigated: (a) imine reduction followed by radical–radical coupling and (b) radical addition followed by product reduction. In addition, investigations to unveil the origin behind the enantioselectivity of the 1-pyrroline derivatives have been conducted as well.

Synthesis of Chiral Amines by C–C Bond Formation with Photoredox Catalysis

Synthesis ◽  
2021 ◽  
Author(s):  
Gregory K. Friestad ◽  
Stephen T. J. Cullen
Keyword(s):  
Radical Addition ◽  
Biologically Active ◽  
Chiral Amines ◽  
Photoredox Catalysis ◽  
Conjugate Additions ◽  
Drug Candidates ◽  
Radical Intermediates ◽  
Radical Coupling ◽  
Amine Oxidation ◽  
Imine Reduction

AbstractChiral amines are key substructures of biologically active natural products and drug candidates. The advent of photoredox catalysis has changed the way synthetic chemists think about building these substructures, opening new pathways that were previously unavailable. New developments in this area are reviewed, with an emphasis on C–C bond constructions involving radical intermediates generated through photoredox processes.1 Introduction2 Radical–Radical Coupling of α-Amino Radicals2.1 Radical–Radical Coupling Involving Amine Oxidation2.2 Radical–Radical Coupling Involving Imine Reduction2.3 Couplings Involving both Amine Oxidation and Imine Reduction3 Addition Reactions of α-Amino Radicals3.1 Conjugate Additions of α-Amino Radicals3.2 Addition of α-Amino Radicals to Heteroaromatic Systems3.3 Cross Coupling via Additions to Transition Metal Complexes4 Radical Addition to C=N Bonds Using Photoredox Catalysis4.1 Intramolecular Radical Addition to C=N Bonds4.2 Intermolecular Radical Addition to C=N Bonds5 Conclusion

scholarly journals Mechanistic insight into B(C6F5)3 catalyzed imine reduction with PhSiH3 under stoichiometric water conditions

RSC Advances ◽  
2021 ◽  
Vol 11 (34) ◽  
pp. 20961-20969
Author(s):  
Yunqing He ◽  
Wanli Nie ◽  
Ying Xue ◽  
Qishan Hu
Keyword(s):  
Mechanistic Insight ◽  
Excess Water ◽  
Water Conditions ◽  
Imine Reduction ◽  
Water Amount ◽  
Insight Into

Hydrosilylation or amination products? It depends on water amount and nucleophiles like excess water or produced/added amines.

Mechanistic Study on Gold(I)-Catalyzed Unsaturated Spiroketalization Reaction

2022 ◽  
Vol 19 ◽  
Author(s):  
Kamlesh Sharma
Keyword(s):  
Activation Barrier ◽  
Ring Formation ◽  
Hydroxyl Group ◽  
Mechanistic Study ◽  
Protecting Group ◽  
Wide Range ◽  
Oxocarbenium Ion ◽  
Metal Catalyzed ◽  
Insight Into ◽  
Mechanism Of The Reaction

Abstract: The mechanism of metal-catalyzed spiroketalization of propargyl acetonide is explored by employing DFT with the B3LYP/6-31+G(d) method. Acetonide is used as a regioselective regulator in the formation of monounsaturated spiroketal. The energies of transition states, intermediates, reactants and products are calculated to provide new insight into the mechanism of the reaction. The energetic features, validation of the observed trends in regioselectivity are conferred in terms of electronic indices via FMO analysis. The presence of acetonide facilitates a stepwise spiroketalization as it masks the competing nucleophile, and thus hydroxyl group present, exclusively acts as a nucleophile. The vinyl gold intermediate 3 is formed from 2 via activation barrier TS1. This is the first ring formation, which is 6-exo-dig cyclization. The intermediate 3 is converted into allenyl ether 4, which isomerizes to the intermediate oxocarbenium ion 5 via activation barrier TS2. The intermediate 5 cyclizes to 6 via TS3. This is the second ring formation. The intermediate 6 on protodeauration turns into 6,6-monounsaturated spiroketal 7. It is concluded that acetonide as a protecting group serves the purpose, and thus a wide range of spiroketals can be prepared, regioselectivity.

Transition metal-free, visible-light-mediated construction of α,β-diamino esters via decarboxylative radical addition at room temperature

2019 ◽  
Vol 6 (13) ◽  
pp. 2245-2249 ◽  
Author(s):  
Guibing Wu ◽  
Jingwen Wang ◽  
Chengyu Liu ◽  
Maolin Sun ◽  
Lei Zhang ◽  
...  
Keyword(s):  
Transition Metal ◽  
Visible Light ◽  
Carboxylic Acids ◽  
Room Temperature ◽  
Radical Addition ◽  
Metal Free ◽  
Radical Coupling

A metal-free photoredox catalyzed decarboxylative radical coupling of free-carboxylic acids and glyoxylic oximes was developed to synthesize α,β-diamino acids.

A computational mechanistic study of substrate-controlled competitive O–H and C–H insertion reactions catalyzed by dirhodium(ii) carbenoids: insight into the origin of chemoselectivity

2018 ◽  
Vol 5 (15) ◽  
pp. 2353-2363 ◽  
Author(s):  
Li-Han Zhu ◽  
Hai-Yan Yuan ◽  
Wen-Liang Li ◽  
Jing-Ping Zhang
Keyword(s):  
Dft Calculations ◽  
Mechanistic Study ◽  
Insertion Reactions ◽  
Rhodium Carbenoid ◽  
Insight Into

DFT calculations disclosed the chemoselectivity of rhodium carbenoid and water co-catalyzed O–H and C–H insertion reactions with three 1,3-diketone substrates.

A New Insight into the Mechanistic Study on Synthesis of Silica Nanospheres

2007 ◽  
Vol 124-126 ◽  
pp. 1249-1252
Author(s):  
Dong Shin Yun ◽  
Hyun Jung Kim ◽  
Hyun Chang Shin ◽  
Venkatathri Narayanan ◽  
Jung Whan Yoo ◽  
...  
Keyword(s):  
Physicochemical Characteristics ◽  
Mechanistic Study ◽  
Partial Hydrolysis ◽  
Particle Sizes ◽  
Species Concentration ◽  
Surface Areas ◽  
Ft Ir ◽  
Alkoxy Groups ◽  
Hydrolysis Of ◽  
Insight Into

The physicochemical characteristics (SEM, N2 adsorption, FT-IR, MASNMR) of samples from kinetics (10 min, 20 min, 30 min, 1 h and 3h) of hydrolysis of tetraethyl orthosilicate (TEOS) gives new insight into the synthesis of nanosphere. The particle sizes are increased with time, however, the surface areas decreased. FT-IR investigation reveals the presence of high intensed silanol groups of 960 cm-1 at 10 min, which reduced on progress of the reaction time. This suggests the partial hydrolysis and condensation of alkoxy groups in TEOS. 29Si MASNMR analysis shows the presence three different silica species(Q4, Q3 and Q2) in 10 and 20 min samples. The intensity of Q2 species decreases with time and other species concentration were increased.

Sign in / Sign up

Export Citation Format

Share Document