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.

Gold nanoparticle as a Lewis acid catalyst in 1,3-dipolar cycloaddition reaction

2020 ◽  
Vol 134 ◽  
pp. 105844
Author(s):  
Hossein Yazdani ◽  
Samira Pardis ◽  
Masood Loni ◽  
Ayoob Bazgir
Keyword(s):  
Gold Nanoparticle ◽  
Lewis Acid ◽  
Cycloaddition Reaction ◽  
Acid Catalyst ◽  
Dipolar Cycloaddition ◽  
Lewis Acid Catalyst

Computationally-Guided Investigation of Dual Amine/pi Lewis Acid Catalysts for Direct Additions of Aldehydes and Ketones to Unactivated Alkenes and Alkynes

2020 ◽  
Author(s):  
Eric Greve ◽  
Jacob D. Porter ◽  
Chris Dockendorff
Keyword(s):  
Lewis Acid ◽  
Density Functional ◽  
Acid Catalyst ◽  
Metal Catalyst ◽  
Catalyst Poisoning ◽  
Lewis Acid Catalysts ◽  
Metal Ligands ◽  
Aldehydes And Ketones ◽  
Lewis Acid Catalyst ◽  
Catalyst Systems

Dual amine/pi Lewis acid catalyst systems have been reported for intramolecular direct additions of aldehydes/ketones to unactivated alkynes and occasionally alkenes, but related intermolecular reactions are rare and not presently of significant synthetic utility, likely due to undesired coordination of enamine intermediates to the metal catalyst. We reasoned that bulky metal ligands and bulky amine catalysts could minimize catalyst poisoning and could facilitate certain examples of direct intermolecular additions of aldehyde/ketones to alkenes/alkynes. Density Functional Theory (DFT) calculations were performed that suggested that PyBOX-Pt(II) catalysts for alkene/alkyne activation could be combined with MacMillan’s imidazolidinone organocatalyst for aldehyde/ketone activation to facilitate desirable C-C bond formations, and certain reactions were calculated to be more exergonic than catalyst poisoning pathways. As calculated, preformed enamines generated from the MacMillan imidazolidinone did not displace ethylene from a biscationic (<i>t</i>-Bu)PyBOX-Pt<sup>2+</sup>complex, but neither were the desired C-C bond formations observed under several different conditions.

Computationally-Guided Investigation of Dual Amine/pi Lewis Acid Catalysts for Direct Additions of Aldehydes and Ketones to Unactivated Alkenes and Alkynes

2020 ◽  
Author(s):  
Eric Greve ◽  
Jacob D. Porter ◽  
Chris Dockendorff
Keyword(s):  
Lewis Acid ◽  
Density Functional ◽  
Acid Catalyst ◽  
Metal Catalyst ◽  
Catalyst Poisoning ◽  
Lewis Acid Catalysts ◽  
Metal Ligands ◽  
Aldehydes And Ketones ◽  
Lewis Acid Catalyst ◽  
Catalyst Systems

Dual amine/pi Lewis acid catalyst systems have been reported for intramolecular direct additions of aldehydes/ketones to unactivated alkynes and occasionally alkenes, but related intermolecular reactions are rare and not presently of significant synthetic utility, likely due to undesired coordination of enamine intermediates to the metal catalyst. We reasoned that bulky metal ligands and bulky amine catalysts could minimize catalyst poisoning and could facilitate certain examples of direct intermolecular additions of aldehyde/ketones to alkenes/alkynes. Density Functional Theory (DFT) calculations were performed that suggested that PyBOX-Pt(II) catalysts for alkene/alkyne activation could be combined with MacMillan’s imidazolidinone organocatalyst for aldehyde/ketone activation to facilitate desirable C-C bond formations, and certain reactions were calculated to be more exergonic than catalyst poisoning pathways. As calculated, preformed enamines generated from the MacMillan imidazolidinone did not displace ethylene from a biscationic (<i>t</i>-Bu)PyBOX-Pt<sup>2+</sup>complex, but neither were the desired C-C bond formations observed under several different conditions.

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.

Computationally-Guided Investigation of Dual Amine/pi Lewis Acid Catalysts for Direct Additions of Aldehydes and Ketones to Unactivated Alkenes and Alkynes

2019 ◽  
Author(s):  
Eric Greve ◽  
Jacob D. Porter ◽  
Chris Dockendorff
Keyword(s):  
Lewis Acid ◽  
Density Functional ◽  
Acid Catalyst ◽  
Metal Catalyst ◽  
Catalyst Poisoning ◽  
Lewis Acid Catalysts ◽  
Metal Ligands ◽  
Aldehydes And Ketones ◽  
Lewis Acid Catalyst ◽  
Catalyst Systems

Dual amine/pi Lewis acid catalyst systems have been reported for intramolecular direct additions of aldehydes/ketones to unactivated alkynes and occasionally alkenes, but related intermolecular reactions are rare and not presently of significant synthetic utility, likely due to undesired coordination of enamine intermediates to the metal catalyst. We reasoned that bulky metal ligands and bulky amine catalysts could minimize catalyst poisoning and could facilitate certain examples of direct intermolecular additions of aldehyde/ketones to alkenes/alkynes. Density Functional Theory (DFT) calculations were performed that suggested that PyBOX-Pt(II) catalysts for alkene/alkyne activation could be combined with MacMillan’s imidazolidinone organocatalyst for aldehyde/ketone activation to facilitate desirable C-C bond formations, and certain reactions were calculated to be more exergonic than catalyst poisoning pathways. As calculated, preformed enamines generated from the MacMillan imidazolidinone did not displace ethylene from a biscationic (<i>t</i>-Bu)PyBOX-Pt<sup>2+</sup>complex, but neither were the desired C-C bond formations observed under several different conditions.

ChemInform Abstract: Study of the Cycloaddition Reaction of Conjugated Oximes with and Without Lewis Acid Catalyst: Dehydrogenation of the Cycloadducts to Isoxazoles.

ChemInform ◽  
2010 ◽  
Vol 28 (12) ◽  
pp. no-no
Author(s):  
R. S. KUSURKAR ◽  
M. S. WADIA ◽  
D. K. BHOSALE ◽  
S. S. TAVALE ◽  
V. G. PURANIK
Keyword(s):  
Lewis Acid ◽  
Cycloaddition Reaction ◽  
Acid Catalyst ◽  
Lewis Acid Catalyst

Mechanism of Lewis-acid-catalyzed intramolecular coupling of sp3C–H bond and alkene: A theoretical investigation

2014 ◽  
Vol 13 (02) ◽  
pp. 1450015
Author(s):  
Miaoqiang Ye ◽  
Rongfu Liu ◽  
Hui Zeng ◽  
Kai Tan ◽  
Xin Lu
Keyword(s):  
Carbon Atom ◽  
Lewis Acid ◽  
Density Functional ◽  
Substituent Effects ◽  
Hydride Transfer ◽  
Acid Catalyst ◽  
First Principle ◽  
Lewis Acid Catalyst ◽  
Acid Catalyzed ◽  
Rate Limiting

First-principle density functional calculations have been carried out to explore the mechanism of the BF 3-catalyzed intramolecular coupling between a C ( sp 3)- H bond in the α-position of such heteroatom as O and an electron-deficient alkene that has an electron-withdrawing substitute, e.g. acetal or carbonyl [McQuaid KM, Sames D, J Am Chem Soc131:402, 2009]. The computations not only confirmed the previously proposed mechanism that coordination of BF 3 (as Lewis acid catalyst) to the acetal oxygen atom triggers 1,5-hydride transfer from the α- C ( sp 3)- H bond to the alkenic carbon, followed by 1,6-cyclization ( C – C bond formation) between the carbon atom of the as-formed oxacarbenium and another alkenic carbon atom, but also disclosed that the 1,5-hydride transfer step is rate-limiting and the cyclization step accounts for the stereoselectivity. In addition, the following substituent effects were disclosed, i.e. the efficacy of intramolecular coupling can be significantly improved by introducing a more electron-donative amino group as the closest neighbor of the hydride donor, but retarded by introducing a less electron-withdrawing – CO 2 Me group as the closest neighbor of the hydride acceptor or by introducing an aromatic phenyl linkage, instead of the saturated linkages exploited in experiments, between the two reacting groups.

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