scholarly journals Silver-catalysed azide–alkyne cycloaddition (AgAAC): assessing the mechanism by density functional theory calculations

2016 ◽  
Vol 3 (9) ◽  
pp. 160090 ◽  
Author(s):  
Biswadip Banerji ◽  
K. Chandrasekhar ◽  
Sunil Kumar Killi ◽  
Sumit Kumar Pramanik ◽  
Pal Uttam ◽  
...  
Keyword(s):  
Density Functional ◽  
Click Reaction ◽  
Cycloaddition Reaction ◽  
Triazole Ring ◽  
Density Functional Theory Calculations ◽  
Dipolar Cycloaddition ◽  
Reaction Conditions ◽  
Functional Theory ◽  
Click Reactions ◽  
Counter Ions

‘Click reactions’ are the copper catalysed dipolar cycloaddition reaction of azides and alkynes to incorporate nitrogens into a cyclic hydrocarbon scaffold forming a triazole ring. Owing to its efficiency and versatility, this reaction and the products, triazole-containing heterocycles, have immense importance in medicinal chemistry. Copper is the only known catalyst to carry out this reaction, the mechanism of which remains unclear. We report here that the ‘click reactions’ can also be catalysed by silver halides in non-aqueous medium. It constitutes an alternative to the well-known CuAAC click reaction. The yield of the reaction varies on the type of counter ion present in the silver salt. This reaction exhibits significant features, such as high regioselectivity, mild reaction conditions, easy availability of substrates and reasonably good yields. In this communication, the findings of a new catalyst along with the effect of solvent and counter ions will help to decipher the still obscure mechanism of this important reaction.

A THEORETICAL STUDY ON THE MECHANISM OF 2:1 1, 3 DIPOLAR CYCLOADDITION REACTIONS

2007 ◽  
Vol 06 (04) ◽  
pp. 861-867 ◽  
Author(s):  
JING-FANG WANG ◽  
DONG-QING WEI ◽  
CHUN-FANG WANG ◽  
YONG YE ◽  
YI-XUE LI ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Organic Synthesis ◽  
Density Functional ◽  
Theoretical Study ◽  
Cycloaddition Reaction ◽  
Density Functional Theory Calculations ◽  
Biologically Active ◽  
Dipolar Cycloaddition ◽  
Functional Theory ◽  
Nitrile Oxides

The reactions between nitrile oxides and alkenes are of considerable interest in organic synthesis as the resulting heterocycles are versatile intermediates for the synthesis of natural products and biologically active compounds. In this paper, we design a series of reactions of phosphonyl nitrile oxides with acrylonnitrile, which can give 2:1 cycloaddition products with no crystal structure released so far, and present a detailed theoretical study on the mechanism of the 2:1 1, 3-dipolar cycloaddition reaction, which has been explored with density functional theory calculations at B3LYP/6-31G* level. The results reveal that the following mechanism is quite possible. Firstly, it starts as a normal 1,3-dipolar cycloaddition reaction to produce a regiospecific 1:1 product. Subsequently, highly reactive diisopropanyl phosphonyl nitrile oxide sequentially reacts with the aforementioned regiospecific 1:1 product and gives the corresponding cycloadduct. Further study is underway to expand the scope of this methodology, as well as to ascertain mechanistic details of the cycloaddition process.

The mechanism of 1,3-dipolar cycloaddition reactions of cyclopropanes and nitrones — A theoretical study

2005 ◽  
Vol 83 (10) ◽  
pp. 1752-1767 ◽  
Author(s):  
D Wanapun ◽  
K A Van Gorp ◽  
N J Mosey ◽  
M A Kerr ◽  
T K Woo
Keyword(s):  
Lewis Acid ◽  
Density Functional ◽  
Cycloaddition Reaction ◽  
Acid Catalyst ◽  
Density Functional Theory Calculations ◽  
Reaction Rates ◽  
Carbonyl Oxygen ◽  
Dipolar Cycloaddition ◽  
Similar Reaction ◽  
Lewis Acid Catalyst

The 1,3-dipolar cycloaddition reaction of cyclopropanes and nitrones to give tetrahydro-1,2-oxazine has been studied with density functional theory calculations at the B3LYP/6-31+G(d,p) level of theory. Realistic substituents were modelled including those at the 2-, 3-, 4-, and 6-positions of the final oxazine ring product. The strained σ bond of the cyclopropane was found to play the role of an alkene in a conventional [3+2] dipolar cycloaddition. Two distinct, but similar, reaction mechanisms were found — an asymmetric concerted pathway and a stepwise zwitterionic pathway. The reaction barriers of the two pathways were nearly identical, differing by less than ~1 kcal/mol, no matter what the substituents were. The effect of a Lewis acid catalyst was examined and found to have a very large effect on the calculated barriers through coordination to the carbonyl oxygen atoms of the diester substituents on the cyclopropane. The reaction barrier was found to decrease by as much as ~19 kcal/mol when using a BF3 molecule as a model for the Lewis acid catalyst. Solvent effects and the nature of the regiospecificity of the reaction were also examined. Trends in the calculated barriers for the reaction were in good agreement with available trends in the reaction rates measured experimentally. Key words: 1,3-dipolar cycloaddition, cyclopropane, nitrone, tetrahydro-1,2-oxazines, ab initio quantum chemistry, mechanism.

DFT interpretations for cycloadditions of an electron deficient C-aryl-N-phenyl nitrone

2014 ◽  
Vol 13 (01) ◽  
pp. 1450007 ◽  
Author(s):  
Nivedita Acharjee
Keyword(s):  
Density Functional ◽  
Transition States ◽  
Density Functional Theory Calculations ◽  
Basis Set ◽  
Dipolar Cycloaddition ◽  
Functional Theory ◽  
Concerted Mechanism ◽  
Reaction Channels ◽  
Calculated Activation Energy ◽  
Calculated Activation

1,3-dipolar cycloaddition reactions of an electron deficient C-aryl-N-phenyl nitrone to benzylidene derivatives (with different electrophilicities) have been analyzed by density functional theory calculations. The transition states corresponding to the endo and exo approaches along the feasible regioisomeric reaction channels have been located for each cycloaddition. The reactions follow a concerted mechanism with asynchronous transition states. The asynchronicity along the regiochemical reaction modes depends on the β-carbon electrophilicities of the olefins. The regio and stereochemistries predicted from the calculated activation energy barriers (with solvent and higher basis set corrections) of the located transition states are in conformity with the experimental results. The local electrophilicities, softness matching indices and the interaction energies were then calculated to analyze how well these reactivity parameters can interpret the regioselectivities of such reactions. The electronic populations at the reactive sites computed from electrostatic potential-driven atomic charges provided correct and consistent predictions for each theoretical model contrary to the natural orbital based charges.

scholarly journals Chemoselective catalytic hydrodefluorination of trifluoromethylalkenes towards mono-/gem-di-fluoroalkenes under metal-free conditions

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Jingjing Zhang ◽  
Jin-Dong Yang ◽  
Jin-Pei Cheng
Keyword(s):  
Density Functional Theory ◽  
Fluorine Atom ◽  
Density Functional ◽  
Density Functional Theory Calculations ◽  
Reaction Conditions ◽  
Functional Theory ◽  
Stepwise Mechanism ◽  
Metal Free ◽  
Great Demand ◽  
Good Group

AbstractFluorine-containing moieties show significant effects in improving the properties of functional molecules. Consequently, efficient methods for installing them into target compounds are in great demand, especially those enabled by metal-free catalysis. Here we show a diazaphospholene-catalyzed hydrodefluorination of trifluoromethylalkenes to chemoselectively construct gem-difluoroalkenes and terminal monofluoroalkenes by simple adjustment of the reactant stoichiometry. This metal-free hydrodefluorination features mild reaction conditions, good group compatibility, and almost quantitative yields for both product types. Stoichiometric experiments indicated a stepwise mechanism: hydridic addition to fluoroalkenes and subsequent β-F elimination from hydrophosphination intermediates. Density functional theory calculations disclosed the origin of chemoselectivity, regioselectivity and stereoselectivity, suggesting an electron-donating effect of the alkene-terminal fluorine atom.

scholarly journals Solvent-controlled photocatalytic divergent cyclization of alkynyl aldehydes: access to cyclopentenones and dihydropyranols

2021 ◽  
Author(s):  
Haiqian Zhu ◽  
Hanliang Zheng ◽  
Junhua Zhang ◽  
Jian Feng ◽  
Lichun Kong ◽  
...  
Keyword(s):  
Density Functional ◽  
Hydrogen Transfer ◽  
Density Functional Theory Calculations ◽  
Bioactive Molecules ◽  
Molecular Scaffolds ◽  
Reaction Conditions ◽  
Direct Construction ◽  
Functional Theory ◽  
Alkoxy Radicals ◽  
Powerful Strategy

Abstract Divergent synthesis is a powerful strategy for the fast assembly of different molecular scaffolds from the identical starting materials. We describe here a novel solvent-controlled photocatalytic divergent cyclization of alkynyl aldehydes with sulfonyl chlorides for the direct construction of highly functionalized cyclopentenones and dihydropyranols that widely exist in bioactive molecules and natural products. Density functional theory calculations suggest that an unprecedented N,N-dimethylacetamide-assisted 1,2-hydrogen transfer of alkoxy radicals is responsible for the cyclopentenone formation, whereas a C-C cleavage accounts for the selective production of dihydropyranols in acetonitrile. Given the simple and mild reaction conditions, excellent functional group compatibility, forming up to four chemical bonds, and tunable selectivity, it may find wide applications in synthetic chemistry.

scholarly journals Investigation of the Reactivity of 1-Azido-3-Iodobicyclo[1.1.1]pentane under “Click” Reaction Conditions

2020 ◽  
Author(s):  
Elisabeth Sitte ◽  
Brendan Twamley ◽  
nitika grover ◽  
Mathias Senge
Keyword(s):  
Click Reaction ◽  
Chemical Properties ◽  
Building Blocks ◽  
Dipolar Cycloaddition ◽  
Coupling Reactions ◽  
Reaction Conditions ◽  
One Pot ◽  
Click Reactions ◽  
Drug Molecules ◽  
Physical And Chemical

The bicyclo[1.1.1]pentane (BCP) unit exhibits special physical and chemical properties and is under scrutiny as a bioisostere in drug molecules. We employed methodologies for the synthesis of different BCP triazole building blocks from one precursor, 1-azido-3-iodobicyclo[1.1.1]pentane, by Cu(I)-catalyzed 1,3-dipolar cycloaddition (“click”) reactions and integrated cycloaddition-Sonogashira coupling reactions. Thereby, we accessed three classes of substituted BCP derivatives: 1,4-disubstituted triazoles, 5-iodo-1,4,5-trisubstituted triazoles and 5-alkynylated 1,4,5-trisubstituted triazoles. This gives entry to the synthesis of multiply substituted BCP triazoles either on a modular or a one-pot basis. These methodologies were further utilized for appending large chromophoric porphyrin moieties onto the BCP core.

scholarly journals Investigation of the Reactivity of 1-Azido-3-Iodobicyclo[1.1.1]pentane under “Click” Reaction Conditions

2020 ◽  
Author(s):  
Elisabeth Sitte ◽  
Brendan Twamley ◽  
nitika grover ◽  
Mathias Senge
Keyword(s):  
Click Reaction ◽  
Chemical Properties ◽  
Building Blocks ◽  
Dipolar Cycloaddition ◽  
Coupling Reactions ◽  
Reaction Conditions ◽  
One Pot ◽  
Click Reactions ◽  
Drug Molecules ◽  
Physical And Chemical

The bicyclo[1.1.1]pentane (BCP) unit exhibits special physical and chemical properties and is under scrutiny as a bioisostere in drug molecules. We employed methodologies for the synthesis of different BCP triazole building blocks from one precursor, 1-azido-3-iodobicyclo[1.1.1]pentane, by Cu(I)-catalyzed 1,3-dipolar cycloaddition (“click”) reactions and integrated cycloaddition-Sonogashira coupling reactions. Thereby, we accessed three classes of substituted BCP derivatives: 1,4-disubstituted triazoles, 5-iodo-1,4,5-trisubstituted triazoles and 5-alkynylated 1,4,5-trisubstituted triazoles. This gives entry to the synthesis of multiply substituted BCP triazoles either on a modular or a one-pot basis. These methodologies were further utilized for appending large chromophoric porphyrin moieties onto the BCP core.

scholarly journals Quantum mechanical investigations of base-catalyzed cycloaddition reaction between phenylacetylene and azidobenzene

2020 ◽  
pp. 174751982094625
Author(s):  
Mohammad Abd Al-Hakim Badawi ◽  
Sultan T Abu-Orabi
Keyword(s):  
Density Functional ◽  
Activation Barrier ◽  
Cycloaddition Reaction ◽  
Product Formation ◽  
Dipolar Cycloaddition ◽  
Kinetic Properties ◽  
Functional Theory ◽  
Rate Determining Step ◽  
Charged System ◽  
The Difference

In this study, the mechanism for both the Huisgen 1,3-dipolar cycloaddition and the base-catalyzed cycloaddition reactions between phenylacetylene and azidobenzene has been investigated with density functional theory, namely at the M06-2X/6-31G(d) computational level. Later, the reaction has been modeled with a representative simple alkyne and a simple azide to concentrate solely on how the difference bases affect the mechanism of the reaction between phenylacetylene and azidobenzene as charged components. In this study, another mechanism of this reaction with uncharged components has been proposed to compare the calculated thermodynamic and kinetic properties for charged and uncharged systems. The calculated activation barrier differences between the catalyzed and the uncatalyzed reactions are consistent with the faster and the regioselective synthesis of the triazole product in the presence of solvents. The calculated barrier of the rate-determining step in the base-catalyzed mechanism with the uncharged system is lower than that with charged systems. Finally, the reaction leading to final product formation in uncharged system is more spontaneous than that in the charged system, and the same applies to the total reaction in the presence of solvents.

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