scholarly journals Unprecedented directed lateral lithiations of tertiary carbons on NHC platforms

2015 ◽  
Vol 51 (15) ◽  
pp. 3049-3052 ◽  
Author(s):  
Andreas A. Danopoulos ◽  
Pierre Braunstein ◽  
Elixabete Rezabal ◽  
Gilles Frison
Keyword(s):  
Dft Calculations ◽  
Heterocyclic Carbenes ◽  
Thermodynamic Control ◽  
Tautomeric Mixture

Deprotonation of the tautomeric mixture of 4-amido-imidazoliums and 4-amino-N-heterocyclic carbenes led to dilithiated dianionic functional NHCs, via an unprecedented regioselective, directed remote lateral lithiation of a tertiary CHMe2 carbon. DFT calculations support that the nature of products is under thermodynamic control.

scholarly journals Catalytic atroposelective synthesis of axially chiral benzonitriles via chirality control during bond dissociation and CN group formation

2022 ◽  
Vol 13 (1) ◽  
Author(s):  
Ya Lv ◽  
Guoyong Luo ◽  
Qian Liu ◽  
Zhichao Jin ◽  
Xinglong Zhang ◽  
...  
Keyword(s):  
Dft Calculations ◽  
Kinetic Resolution ◽  
Group Formation ◽  
Heterocyclic Carbenes ◽  
Large Set ◽  
Dynamic Kinetic Resolution ◽  
Catalytic Activities ◽  
Bond Dissociation ◽  
Axially Chiral ◽  
Chirality Control

AbstractThe applications of axially chiral benzonitriles and their derivatives remain mostly unexplored due to their synthetic difficulties. Here we disclose an unusual strategy for atroposelective access to benzonitriles via formation of the nitrile unit on biaryl scaffolds pre-installed with stereogenic axes in racemic forms. Our method starts with racemic 2-arylbenzaldehydes and sulfonamides as the substrates and N-heterocyclic carbenes as the organocatalysts to afford axially chiral benzonitriles in good to excellent yields and enantioselectivities. DFT calculations suggest that the loss of p-toluenesulfinate group is both the rate-determining and stereo-determining step. The axial chirality is controlled during the bond dissociation and CN group formation. The reaction features a dynamic kinetic resolution process modulated by both covalent and non-covalent catalytic interactions. The axially chiral benzonitriles from our method can be easily converted to a large set of functional molecules that show promising catalytic activities for chemical syntheses and anti-bacterial activities for plant protections.

scholarly journals From Chlorosilyliumylidene Complexes to Cyclic Silylones with an Electron-Rich Silicon(0) Atom

2014 ◽  
Author(s):  
Yun Xiong ◽  
Shenglai Yao ◽  
Shigeyoishi Inoue ◽  
Jan Dirk Epping ◽  
Matthias Driess
Keyword(s):  
Dft Calculations ◽  
Heterocyclic Carbenes ◽  
Homo And Lumo ◽  
Neutral Bidentate ◽  
Sodium Naphthalenide ◽  
Significant Attention

Molecular silicon(0) species L→Si←L (L = N-heterocyclic carbenes, phosphanes, etc.), termed as silylones, have attracted significant attention. By employing the neutral bidentate bis-NHC ligand the unprecedented bis(carbene) chlorosilyliumylidene complex 1 could be isolated, in which both HOMO and LUMO are mainly localized on the silicon(II) atom according to DFT calculations./1/ Thus, dechlorination of 1 by sodium naphthalenide led to the first isolable cyclic silylone (siladicarbene) 2 featuring an electron-rich silicon(0) atom due to the weak π-acceptor character of the NHC supporting ligand.

scholarly journals NHC-catalyzed Enantioselective Hetero-[10+2] Annulation

2020 ◽  
Author(s):  
Jian wang ◽  
Qiupeng Peng ◽  
shi-jun li ◽  
Bei Zhang ◽  
Donghui Guo ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Dft Calculations ◽  
Asymmetric Synthesis ◽  
Density Functional ◽  
Higher Order ◽  
Heterocyclic Carbenes ◽  
Wide Scope ◽  
Functional Theory ◽  
One Step ◽  
High Yields

Abstract The higher-order cycloadditions are powerful strategies for construction of polycycles in one step, however an efficient and concise version for asymmetric induce is limited. N-heterocyclic carbenes are widely used organocatalysts for asymmetric synthesis and will be an ideal choice for enantioselective higher-order cycloadditions. Here we report an enantioselective [10+2] annulation between catalytically formed aza-benzofulvene intermediates and trifluoromethyl ketone derivatives. This protocol exhibits a wide scope, high yields and good ee values, reflecting a robust and efficient higher-order cycloaddition. Density functional theory (DFT) calculations provided an accurate prediction of the reaction enantioselectivity, and in-depth insight to the origins of stereocontrol.

Different electronic structure of phosphonyl radical adducts of N-heterocyclic carbenes, silylenes and germylenes: EPR spectroscopic study and DFT calculations

2010 ◽  
Vol 1 (2) ◽  
pp. 234 ◽  
Author(s):  
Dennis Sheberla ◽  
Boris Tumanskii ◽  
Adam C. Tomasik ◽  
Amitabha Mitra ◽  
Nicholas J. Hill ◽  
...  
Keyword(s):  
Electronic Structure ◽  
Dft Calculations ◽  
Spectroscopic Study ◽  
Heterocyclic Carbenes ◽  
Phosphonyl Radical

Structure elucidation of a proton-deficient natural product using LR-HSQMBC supported by DFT calculations

Planta Medica ◽  
2015 ◽  
Vol 81 (11) ◽  
Author(s):  
J Saurí ◽  
STS Chan ◽  
AV Buevich ◽  
KR Gustafson ◽  
RT Williamson ◽  
...  
Keyword(s):  
Dft Calculations ◽  
Natural Product ◽  
Structure Elucidation

Stereodivergent Alkyne Hydrofluorination Using a Simple Practical Reagent

2020 ◽  
Author(s):  
Rui Guo ◽  
Xiaotian Qi ◽  
Hengye Xiang ◽  
Paul Geaneoates ◽  
Ruihan Wang ◽  
...  
Keyword(s):  
Bond Formation ◽  
Biologically Active ◽  
Dft Studies ◽  
Thermodynamic Control ◽  
Important Goal ◽  
Peptide Bonds ◽  
Metal Free ◽  
Vinyl Cation ◽  
E And Z Isomers ◽  
Vinyl Fluorides

Vinyl fluorides play an important role in drug development as they serve as bioisosteres for peptide bonds and are found in a range of biologically active molecules. The discovery of safe, general and practical procedures to prepare vinyl fluorides remains an important goal and challenge for synthetic chemistry. Here we introduce an inexpensive and easily-handled reagent and report simple, scalable, and metal-free protocols for the regioselective and stereodivergent hydrofluorination of alkynes to access both the E and Z isomers of vinyl fluorides. These conditions were suitable for a diverse collection of alkynes, including several highly-functionalized pharmaceutical derivatives. Mechanistic and DFT studies support C–F bond formation through a vinyl cation intermediate, with the (E)- and (Z)-hydrofluorination products forming under kinetic and thermodynamic control, respectively.<br>

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