Reactions of β-diketone compounds with nitriles catalyzed by Lewis acids: a simple approach to β-enaminone synthesis

RSC Advances ◽  
2014 ◽  
Vol 4 (109) ◽  
pp. 63897-63900 ◽  
Author(s):  
Xu Cheng ◽  
Shuchen Pei ◽  
Chenchen Xue ◽  
Kaifei Cao ◽  
Li Hai ◽  
...  
Keyword(s):  
Lewis Acids ◽  
Simple Approach ◽  
Aluminium Chloride ◽  
Nucleophilic Attack

Aluminium chloride selectively promoted the nucleophilic attack of β-diketone compounds with nitriles to give enaminones.

scholarly journals Orthoamide, LXIII [1]. Tris(dichlormethyl)amin, ein neues breit anwendbares Formylierungsmittel für Aromaten / Orthoamides, LXIII [1]. Tris(dichloromethyl)amine, a New Formylating Reagent for Aromatic Compounds of Wide Scope

2006 ◽  
Vol 61 (4) ◽  
pp. 448-463 ◽  
Author(s):  
Willi Kantlehner ◽  
Ralf Kreß ◽  
Franziska Zschach ◽  
Jens Vetter ◽  
Georg Ziegler ◽  
...  
Keyword(s):  
Aluminum Chloride ◽  
Aromatic Compounds ◽  
Lewis Acids ◽  
Aluminium Chloride ◽  
Aromatic Nucleus ◽  
Wide Scope ◽  
Formyl Group ◽  
Reaction Conditions ◽  
Optimal Reaction

The reagent system formed from tris(dichloromethyl)amine (5) and aluminium chloride allows the formylation of aromatic compounds. The scope of the method is comparable with that of the Olah formylation and the Groß-Rieche procedure, since benzene and even chlorobenzene can be formylated. One formyl group is transferred from 5 to the aromatic nucleus. In order to find optimal reaction conditions, the molar amounts of aromatic compounds, 5 and aluminum chloride were varied as well as reaction temperatures and solvents. The activation of 5 with other Lewis acids is also described

scholarly journals Role of Lewis Acids in Preventing the Degradation of Dithioester-Dormant Species in the RAFT Polymerization of Acrylamides in Methanol to Enable the Successful Dual Control of Molecular Weight and Tacticity

2021 ◽  
Author(s):  
Yuji Imamura ◽  
Shigeru Yamago
Keyword(s):  
Molecular Weight ◽  
Lewis Acids ◽  
Chain Transfer ◽  
Raft Polymerization ◽  
Degradation Mechanism ◽  
Earth Metal ◽  
Nucleophilic Attack ◽  
Molecular Weights ◽  
Reversible Addition ◽  
Metal Triflates

Reversible addition-fragmentation chain transfer (RAFT) polymerization of acrylamide in methanol using dithioester RAFT chain-transfer agents was unsuccessful due to degradation of the end group. However, this degradation was completely suppressed by the addition of rare-earth metal triflates (RMTs). As RMTs are effective for the stereoselective polymerization of acrylamides, RAFT polymerization in the presence of RMTs afforded the corresponding poly(acrylamide)s with controlled molecular weight and tacticity. The conditions allowed the synthesis of high-molecular-weight polyacrylamides with molecular weights up to 168,000, low dispersity (<1.5) and high tacticity (90% <i>meso</i> diad selectivity). The degradation mechanism initiated by nucleophilic attack of acrylamide on the dithioester group was experimentally clarified for the first time. As RMT is a Lewis acid, its coordination to the amide group of acrylamide reduces its nucleophilicity.

scholarly journals Role of Lewis Acids in Preventing the Degradation of Dithioester-Dormant Species in the RAFT Polymerization of Acrylamides in Methanol to Enable the Successful Dual Control of Molecular Weight and Tacticity

2021 ◽  
Author(s):  
Yuji Imamura ◽  
Shigeru Yamago
Keyword(s):  
Molecular Weight ◽  
Lewis Acids ◽  
Chain Transfer ◽  
Raft Polymerization ◽  
Degradation Mechanism ◽  
Earth Metal ◽  
Nucleophilic Attack ◽  
Molecular Weights ◽  
Reversible Addition ◽  
Metal Triflates

Reversible addition-fragmentation chain transfer (RAFT) polymerization of acrylamide in methanol using dithioester RAFT chain-transfer agents was unsuccessful due to degradation of the end group. However, this degradation was completely suppressed by the addition of rare-earth metal triflates (RMTs). As RMTs are effective for the stereoselective polymerization of acrylamides, RAFT polymerization in the presence of RMTs afforded the corresponding poly(acrylamide)s with controlled molecular weight and tacticity. The conditions allowed the synthesis of high-molecular-weight polyacrylamides with molecular weights up to 168,000, low dispersity (<1.5) and high tacticity (90% <i>meso</i> diad selectivity). The degradation mechanism initiated by nucleophilic attack of acrylamide on the dithioester group was experimentally clarified for the first time. As RMT is a Lewis acid, its coordination to the amide group of acrylamide reduces its nucleophilicity.

Asymmetric synthesis based on chiral (arene)tricarbonylchromium acetal complexes. Addition reactions to the ortho-formyl complex

2000 ◽  
Vol 78 (12) ◽  
pp. 1629-1636 ◽  
Author(s):  
M Kevin McKay ◽  
James R Green
Keyword(s):  
Asymmetric Synthesis ◽  
Lewis Acid ◽  
Lewis Acids ◽  
Nucleophilic Attack ◽  
Addition Reactions ◽  
Trans Conformation ◽  
Enantiomerically Pure ◽  
The Face ◽  
Monodentate Coordination ◽  
Tricarbonylchromium Complexes

The addition reactions of organolithium and Grignard reagents to chiral, enantiomerically pure ortho-formyl (arene)tricarbonylchromium acetal complex (2) have been studied. The diastereoselectivity of the addition process is fair in the absence of an additional Lewis acid, and good in the presence of Ti(OiPr)4. The nature of the newly formed chiral centre, and studies on the possible nature of the nucleophilic species suggest that the Lewis acid acts through monodentate coordination to the aldehyde carbonyl, and thereby alters the carbonyl rotamer population more heavily in favour of the s-trans conformation. Nucleophilic attack then occurs on the face anti- to that bearing the Cr(CO)3 unit.Key words: (arene)tricarbonylchromium complexes, asymmetric synthesis, carbonyl additions, Lewis acids.

Structure of donor-acceptor complexes. X. Complexes of cyanoacetamide with Lewis acids

1969 ◽  
Vol 22 (7) ◽  
pp. 1381 ◽  
Author(s):  
RC Paul ◽  
SL Chadha
Keyword(s):  
Oxygen Atom ◽  
Spectral Data ◽  
Infrared Spectra ◽  
Lewis Acids ◽  
Far Infrared ◽  
Carbonyl Oxygen ◽  
Aluminium Chloride ◽  
Infrared Spectral ◽  
Donor Acceptor ◽  
Ionic Nature

Complexes of cyanoacetamide with aluminium chloride and bromide, anti- mony(V) chloride, boron(III) bromide, tin(IV) chloride and bromide, titanium(IV) chloride and bromide, and zirconium(IV) chloride have been prepared. The molar conductances of the complexes in nitrobenzene indicate their non-ionic nature. The infrared spectra indicate bonding of the metal halides to the carbonyl oxygen atom of the ligand. Metal- to-oxygen bonding also gets support from the far-infrared spectral data.

scholarly journals Amphoteric Lewis Acid/base Activity Enables an Unprecedented Pathway for Low-Energy C-O Cleavage in the Electrocatalytic Reduction of Carbon Dioxide

2021 ◽  
Author(s):  
Hemlata Agarwala ◽  
Xiaoyu Chen ◽  
Julien R. Lyonnet ◽  
Ben A Johnson ◽  
Mårten Ahlquist ◽  
...  
Keyword(s):  
Lewis Acid ◽  
Lewis Acids ◽  
Density Functional ◽  
Activation Barrier ◽  
Bond Cleavage ◽  
Lewis Base ◽  
Nucleophilic Attack ◽  
Co Conversion ◽  
Energy Conserving ◽  
Ft Ir

Molecular electrocatalysts for CO<sub>2</sub>-to-CO conversion often operate at large overpotentials, the cleavage of C-O bond in the intermediate largely contributing to this phenomenon. Additional Lewis acids have been shown to aid in weakening the C-O bond. We herein present computational and experimental evidence, with ruthenium polypyridyl based CO<sub>2</sub> reduction electrocatalysts, for a mechanistic route that involves one metal center acting as both Lewis base and Lewis acid at different stages of the catalytic cycle. The Lewis basic character of Ru is seen in the initial nucleophilic attack at CO<sub>2</sub> to form [<b>Ru</b>-CO<sub>2</sub>]<sup>0</sup>, while its Lewis acid character allows the formation of a 5-membered metallacyclic intermediate, [<b>Ru</b>-CO<sub>2</sub>CO<sub>2</sub>]<sup>0,c</sup>, by intramolecular cyclization of a linear [<b>Ru</b>-CO<sub>2</sub>CO<sub>2</sub>]<sup>0</sup> species that is formed from [<b>Ru</b>-CO<sub>2</sub>]<sup>0</sup> and a second equivalent of CO<sub>2</sub>. [<b>Ru</b>-CO<sub>2</sub>CO<sub>2</sub>]<sup>0,c</sup> is crucial for energy-conserving turnover, as it allows for a third reduction at a more positive potential than that of the starting complex <b>Ru</b><sup>2+</sup>. The calculated activation barrier for C-O bond cleavage in [<b>Ru</b>-CO<sub>2</sub>CO<sub>2</sub>]<sup>-1,c</sup> is dramatically decreased to 10.5 kcal mol<sup>-1</sup> from 60 kcal mol<sup>-1</sup>, the latter required for C-O bond cleavage in the linear intermediate [<b>Ru</b>-CO<sub>2</sub>CO<sub>2</sub>]<sup>0</sup>. The intermediates are characterized experimentally by FT-IR and <sup>13</sup>C NMR spectroscopy during electrocatalytic turnover and are corroborated by density functional theory (DFT).<br>

Cyclisation intramoléculaire des acides benzyl-2 pentène-4 oïques. Préparation de quelques tétraméthylnaphtalènes

1967 ◽  
Vol 45 (11) ◽  
pp. 1267-1274 ◽  
Author(s):  
P. Canonne ◽  
A. Regnault
Keyword(s):  
Lewis Acids ◽  
Aluminium Chloride ◽  
Methyl Groups ◽  
Secondary Reactions

The cyclization of 2-benzyl-4-pentenoic acids, catalyzed by protonic and Lewis acids, resulted in the formation of variable quantities of α-benzyl-γ-valerolactones and tetrahydronaphthalenecarboxylic acids (65 – 85%) which, after reduction and dehydrogenation, yielded tetramethylnaphthalenes substituted in the 1,3-positions. 1,3,5,7-Tetramethylnaphthalene, in particular, had not as yet been described. Aluminium chloride favors cyclization and does not give rise to lactonization, but it induces secondary reactions such as the migration of methyl groups.

scholarly journals Amphoteric Lewis Acid/base Activity Enables an Unprecedented Pathway for Low-Energy C-O Cleavage in the Electrocatalytic Reduction of Carbon Dioxide

2021 ◽  
Author(s):  
Hemlata Agarwala ◽  
Xiaoyu Chen ◽  
Julien R. Lyonnet ◽  
Ben A Johnson ◽  
Mårten Ahlquist ◽  
...  
Keyword(s):  
Lewis Acid ◽  
Lewis Acids ◽  
Density Functional ◽  
Activation Barrier ◽  
Bond Cleavage ◽  
Lewis Base ◽  
Nucleophilic Attack ◽  
Co Conversion ◽  
Energy Conserving ◽  
Ft Ir

Molecular electrocatalysts for CO<sub>2</sub>-to-CO conversion often operate at large overpotentials, the cleavage of C-O bond in the intermediate largely contributing to this phenomenon. Additional Lewis acids have been shown to aid in weakening the C-O bond. We herein present computational and experimental evidence, with ruthenium polypyridyl based CO<sub>2</sub> reduction electrocatalysts, for a mechanistic route that involves one metal center acting as both Lewis base and Lewis acid at different stages of the catalytic cycle. The Lewis basic character of Ru is seen in the initial nucleophilic attack at CO<sub>2</sub> to form [<b>Ru</b>-CO<sub>2</sub>]<sup>0</sup>, while its Lewis acid character allows the formation of a 5-membered metallacyclic intermediate, [<b>Ru</b>-CO<sub>2</sub>CO<sub>2</sub>]<sup>0,c</sup>, by intramolecular cyclization of a linear [<b>Ru</b>-CO<sub>2</sub>CO<sub>2</sub>]<sup>0</sup> species that is formed from [<b>Ru</b>-CO<sub>2</sub>]<sup>0</sup> and a second equivalent of CO<sub>2</sub>. [<b>Ru</b>-CO<sub>2</sub>CO<sub>2</sub>]<sup>0,c</sup> is crucial for energy-conserving turnover, as it allows for a third reduction at a more positive potential than that of the starting complex <b>Ru</b><sup>2+</sup>. The calculated activation barrier for C-O bond cleavage in [<b>Ru</b>-CO<sub>2</sub>CO<sub>2</sub>]<sup>-1,c</sup> is dramatically decreased to 10.5 kcal mol<sup>-1</sup> from 60 kcal mol<sup>-1</sup>, the latter required for C-O bond cleavage in the linear intermediate [<b>Ru</b>-CO<sub>2</sub>CO<sub>2</sub>]<sup>0</sup>. The intermediates are characterized experimentally by FT-IR and <sup>13</sup>C NMR spectroscopy during electrocatalytic turnover and are corroborated by density functional theory (DFT).<br>

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