Yttrium dialkyl supported by a silaamidinate ligand: synthesis, structure and catalysis on cyclotrimerization of isocyanates

2019 ◽  
Vol 55 (82) ◽  
pp. 12324-12327
Author(s):  
Deshuai Liu ◽  
Dahai Zhou ◽  
Hao Yang ◽  
Jianfeng Li ◽  
Chunming Cui
Keyword(s):  
High Activity ◽  
Functional Group ◽  
Sterically Demanding ◽  
Ligand Synthesis

A four-coordinate yttrium dialkyl complex with a sterically demanding silaamidinate ligand exhibited high activity and excellent functional group tolerance for the catalysis of isocyanate cyclotrimerization.

Iridium-Catalyzed Silylation of C-H bonds in Unactivated Arenes: A Sterically-Encumbered Phenanthroline Ligand Accelerates Catalysis Enabling New Reactivity

2019 ◽  
Author(s):  
Caleb Karmel ◽  
Zhewei Chen ◽  
John Hartwig
Keyword(s):  
High Activity ◽  
Functional Group ◽  
Activity Analysis ◽  
High Reactivity ◽  
High Yield ◽  
Phen Ligand ◽  
Mechanistic Studies ◽  
Phenanthroline Ligand ◽  
First Time ◽  
New System

We report a new system for the silylation of aryl C-H bonds. The combination of [Ir(cod)(OMe)]<sub>2</sub> and 2,9-Me<sub>2</sub>-phenanthroline (2,9-Me<sub>2</sub>phen) catalyzes the silylation of arenes at lower temperatures and with faster rates than those reported previously, when the hydrogen byproduct is removed, and with high functional group tolerance and regioselectivity. Inhibition of reactions by the H<sub>2</sub> byproduct is shown to limit the silylation of aryl C-H bonds in the presence of the most active catalysts, thereby masking their high activity. Analysis of initial rates uncovered the high reactivity of the catalyst containing the sterically hindered 2,9-Me<sub>2</sub>phen ligand but accompanying rapid inhibition by hydrogen. With this catalyst, under a flow of nitrogen to remove hydrogen, electron-rich arenes, including those containing sensitive functional groups, undergo silylation in high yield for the first time, and arenes that underwent silylation with prior catalysts react over much shorter times with lower catalyst loadings. The synthetic value of this methodology is demonstrated by the preparation of key intermediates in the synthesis of medicinally important compounds in concise sequences comprising silylation and functionalization. Mechanistic studies demonstrate that the cleavage of the aryl C-H bond is reversible and that the higher rates observed with the 2,9-Me<sub>2</sub>phen ligand is due to a more thermodynamically favorable oxidative addition of aryl C-H bonds.

Palladium-Catalyzed Arylation of Aromatic Amides Directed by a [4-Chloro-2-(1H-pyrazol-1-yl)phenyl]amine Auxiliary

Synlett ◽  
2018 ◽  
Vol 29 (14) ◽  
pp. 1875-1880 ◽  
Author(s):  
Ya-Fei Ji ◽  
Ya-Hua Hu ◽  
Zhi Xu ◽  
Ling-Yan Shao
Keyword(s):  
Working Conditions ◽  
Functional Group ◽  
Aryl Iodide ◽  
Sterically Demanding ◽  
Palladium Catalyzed

A palladium-catalyzed ortho-arylation of aromatic amides ­directed by [4-chloro-2-(1H-pyrazol-1-yl)phenyl]amine as a bidentate auxiliary has been established. The reaction is characterized by normal working conditions, a broad substrate scope, and a wide functional-group tolerance. In particular, the protocol is compatible with highly sterically demanding ortho-substituted anilides and aryl iodide partners, with good yields.

Iridium-Catalyzed Silylation of C-H bonds in Unactivated Arenes: A Sterically-Encumbered Phenanthroline Ligand Accelerates Catalysis Enabling New Reactivity

2019 ◽  
Author(s):  
Caleb Karmel ◽  
Zhewei Chen ◽  
John Hartwig
Keyword(s):  
High Activity ◽  
Functional Group ◽  
Activity Analysis ◽  
High Reactivity ◽  
High Yield ◽  
Phen Ligand ◽  
Mechanistic Studies ◽  
Phenanthroline Ligand ◽  
First Time ◽  
New System

We report a new system for the silylation of aryl C-H bonds. The combination of [Ir(cod)(OMe)]<sub>2</sub> and 2,9-Me<sub>2</sub>-phenanthroline (2,9-Me<sub>2</sub>phen) catalyzes the silylation of arenes at lower temperatures and with faster rates than those reported previously, when the hydrogen byproduct is removed, and with high functional group tolerance and regioselectivity. Inhibition of reactions by the H<sub>2</sub> byproduct is shown to limit the silylation of aryl C-H bonds in the presence of the most active catalysts, thereby masking their high activity. Analysis of initial rates uncovered the high reactivity of the catalyst containing the sterically hindered 2,9-Me<sub>2</sub>phen ligand but accompanying rapid inhibition by hydrogen. With this catalyst, under a flow of nitrogen to remove hydrogen, electron-rich arenes, including those containing sensitive functional groups, undergo silylation in high yield for the first time, and arenes that underwent silylation with prior catalysts react over much shorter times with lower catalyst loadings. The synthetic value of this methodology is demonstrated by the preparation of key intermediates in the synthesis of medicinally important compounds in concise sequences comprising silylation and functionalization. Mechanistic studies demonstrate that the cleavage of the aryl C-H bond is reversible and that the higher rates observed with the 2,9-Me<sub>2</sub>phen ligand is due to a more thermodynamically favorable oxidative addition of aryl C-H bonds.

NHC-Catalyzed Synthesis of Benzazole-Phosphine Ligands under an Air Atmosphere

Synlett ◽  
2019 ◽  
Vol 30 (14) ◽  
pp. 1719-1724
Author(s):  
Wei Ren ◽  
Qian-Ming Zuo ◽  
Shang-Dong Yang
Keyword(s):  
Functional Group ◽  
Oxidative Cyclization ◽  
Phosphine Ligand ◽  
Phosphine Ligands ◽  
Cyclization Reaction ◽  
Atom Economy ◽  
Efficient Strategy ◽  
Air Atmosphere ◽  
Ligand Precursors ◽  
Ligand Synthesis

An efficient strategy for the synthesis of benzazole-phosphine ligand precursors via N-heterocyclic carbene catalyzed aerobic oxidative cyclization reaction has been performed. The reaction displays broad functional group tolerance and high atom economy, and the transformation has been further applied to benzazole-phosphine ligand synthesis.

scholarly journals Iridium-catalyzed selective 1,2-hydrosilylation of N-heterocycles

2016 ◽  
Vol 7 (8) ◽  
pp. 5362-5370 ◽  
Author(s):  
Jinseong Jeong ◽  
Sehoon Park ◽  
Sukbok Chang
Keyword(s):  
High Activity ◽  
Functional Group ◽  
Excellent Selectivity

A silylene-bridged Ir dimer in situ generated from [Ir(coe)2Cl]2 and Et2SiH2 was found to catalyze the hydrosilylation of N-heteroaromatics to furnish dearomatized azacyclic products with high activity (up to 1000 TONs), excellent selectivity, and good functional group tolerance.

Bis(amidinato)- and bis(guanidinato)silylenes and silylenes with one sterically demanding amidinato or guanidinato ligand: synthesis and reactivity

2017 ◽  
Vol 46 (40) ◽  
pp. 13628-13659 ◽  
Author(s):  
Reinhold Tacke ◽  
Tatjana Ribbeck
Keyword(s):  
Structural Motifs ◽  
Sterically Demanding ◽  
Ligand Synthesis

Silylenes 1–4 have great synthetic potential for the synthesis of higher coordinate silicon(ii) and silicon(iv) complexes with unprecedented structural motifs.

First-row early transition metal complexes with a highly sterically demanding triisopropylphenyl amino triphenolate ligand: synthesis and applications

2019 ◽  
Vol 48 (26) ◽  
pp. 9617-9624 ◽  
Author(s):  
Dae Young Bae ◽  
Gyeong Su Park ◽  
Nakeun Ko ◽  
Kyung-sun Son ◽  
Eunsung Lee
Keyword(s):  
Transition Metal ◽  
Metal Complexes ◽  
Transition Metal Complexes ◽  
Early Transition Metal ◽  
Sterically Demanding ◽  
Ligand Synthesis ◽  
Early Transition

A highly sterically demanding amino triphenolate ligand was successfully synthesized, and early transition metal complexes (Ti, V, Cr, and Mn) supported by the ligand were also obtained and fully characterized.

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