Investigation of catalytic effects of the proton and Lewis acids on oligomerization and chemical polymerization of pyrrole

Polymer ◽  
2004 ◽  
Vol 45 (20) ◽  
pp. 7011-7016 ◽  
Author(s):  
Muzaffer Can ◽  
Hayri Özaslan ◽  
Ömer Işıldak ◽  
Nuran Ö Pekmez ◽  
Attila Yıldız
Keyword(s):  
Lewis Acids ◽  
Chemical Polymerization ◽  
Catalytic Effects

Efficient Catalytic Effects of Lewis Acids in the 1,3-Dipolar Cycloaddition Reactions of Carbonyl Ylides with Imines

2005 ◽  
Vol 70 (26) ◽  
pp. 10782-10791 ◽  
Author(s):  
Hiroyuki Suga ◽  
Yasutaka Ebiura ◽  
Kazuaki Fukushima ◽  
Akikazu Kakehi ◽  
Toshihide Baba
Keyword(s):  
Lewis Acids ◽  
Dipolar Cycloaddition ◽  
Cycloaddition Reactions ◽  
Catalytic Effects

HALOGEN MIGRATION AND ELIMINATION IN THE CLAISEN REARRANGEMENT OF ALLYL 2,6-DIHALOPHENYL ETHERS

1963 ◽  
Vol 41 (12) ◽  
pp. 2917-2930 ◽  
Author(s):  
E. Piers ◽  
R. K. Brown
Keyword(s):  
Dielectric Constant ◽  
Lewis Acids ◽  
Claisen Rearrangement ◽  
Stannous Chloride ◽  
Ionic Species ◽  
Thermal Rearrangement ◽  
Polar Solvents ◽  
Factors Affecting ◽  
Competitive Reduction ◽  
Catalytic Effects

A study has been made of some factors affecting the migration or elimination of halogen in the Claisen rearrangement of allyl 2,6-dihalophenyl ethers.In the thermal rearrangement of allyl 2,6-dichlorophenyl ether, carried out in a number of solvents of different dielectric constant, halogen migration proceeds somewhat better in highly polar solvents. However, a competitive reduction to the monohalogenated allylphenol occurs in the presence of oxidizable solvents and/or products. The reaction is also complicated by the catalytic effects of certain solvents and the phenolic products, which give results similar to those obtained with Lewis acids. Stannous chloride acts as a Lewis acid and catalyzes the rearrangement of allyl 2,6-dichlorophenyl ether with simultaneous halogen rearrangement. As well, a competitive reductive removal of the halogen takes place. Results from the rearrangement of allyl 2,6-dibromophenyl ether with zinc chloride and of allyl 2,6-dichlorophenyl ether with zinc bromide, as well as those from the stannous chloride reactions indicate that the halogen migration takes place not only by an allylic shift but also via a competitive halogen substitution probably occurring by an Sn2′ pathway possibly assisted by a zinc halide bridge mechanism and/or an ionic species such as [Formula: see text].

Catalytic effects of Lewis acids on 1,3-DC reaction: A luminescent study

2012 ◽  
Vol 132 (6) ◽  
pp. 1456-1461 ◽  
Author(s):  
Tandrima Chaudhuri ◽  
Manas Banerjee
Keyword(s):  
Lewis Acids ◽  
Catalytic Effects

scholarly journals Highly Efficient Synthesis of Substituted 3,4-Dihydropyrimidin-2-(1H)-ones (DHPMs) Catalyzed by Hf(OTf)4: Mechanistic Insights into Reaction Pathways under Metal Lewis Acid Catalysis and Solvent-Free Conditions

Molecules ◽  
2019 ◽  
Vol 24 (2) ◽  
pp. 364 ◽  
Author(s):  
Rui Kong ◽  
Shuai-Bo Han ◽  
Jing-Ying Wei ◽  
Xiao-Chong Peng ◽  
Zhen-Biao Xie ◽  
...  
Keyword(s):  
Lewis Acids ◽  
Synergistic Effects ◽  
Biginelli Reaction ◽  
Mechanistic Explanation ◽  
Solvent Free ◽  
Reaction Pathways ◽  
Methyl Acetoacetate ◽  
One Pot ◽  
Solvent Free Conditions ◽  
Catalytic Effects

In our studies on the catalytic activity of Group IVB transition metal Lewis acids, Hf(OTf)4 was identified as a highly potent catalyst for ”one-pot, three-component” Biginelli reaction. More importantly, it was found that solvent-free conditions, in contrast to solvent-based conditions, could dramatically promote the Hf(OTf)4-catalyzed formation of 3,4-dihydro-pyrimidin-2-(1H)-ones. To provide a mechanistic explanation, we closely examined the catalytic effects of Hf(OTf)4 on all three potential reaction pathways in both “sequential bimolecular condensations” and “one-pot, three-component” manners. The experimental results showed that the synergistic effects of solvent-free conditions and Hf(OTf)4 catalysis not only drastically accelerate Biginelli reaction by enhancing the imine route and activating the enamine route but also avoid the formation of Knoevenagel adduct, which may lead to an undesired byproduct. In addition, 1H-MMR tracing of the H-D exchange reaction of methyl acetoacetate in MeOH-d4 indicated that Hf(IV) cation may significantly accelerate ketone-enol tautomerization and activate the β-ketone moiety, thereby contributing to the overall reaction rate.

scholarly journals Efficient Catalytic Effects of Lewis Acids in the 1,3-Dipolar Cycloaddition Reactions of Carbonyl Ylides with Imines.

ChemInform ◽  
2006 ◽  
Vol 37 (19) ◽  
Author(s):  
Hiroyuki Suga ◽  
Yasutaka Ebiura ◽  
Kazuaki Fukushima ◽  
Akikazu Kakehi ◽  
Toshihide Baba
Keyword(s):  
Lewis Acids ◽  
Dipolar Cycloaddition ◽  
Cycloaddition Reactions ◽  
Catalytic Effects

Decomposition of peroxobenzoic acid in benzene catalyzed by transition metal 2,4-pentanedionates

1984 ◽  
Vol 49 (3) ◽  
pp. 673-679 ◽  
Author(s):  
Pavel Lederer ◽  
Eva Mácová ◽  
Josef Vepřek-Šiška
Keyword(s):  
Transition Metal ◽  
Reaction Rate ◽  
Reaction Products ◽  
Acid Decomposition ◽  
Analogous Experiment ◽  
Catalytic Effects

The decomposition of peroxobenzoic acid in benzene was studied, and catalytic effects of Fe(III), Mn(III), Co(II), Co(III), and Cr(III) on the reaction rate and the composition of the reaction mixture were investigated. An analogous experiment carried out in perdeuterobenzene and determination of the distribution of deuterium in the reaction products provided evidence for the participation of the solvent in peroxobenzoic acid decomposition.

scholarly journals Theoretical Insight into the Reversal of Chemoselectivity in Diels-Alder Reactions of α,β-Unsaturated Aldehydes and Ketones Catalyzed by Brønsted and Lewis Acids

Organics ◽  
2021 ◽  
Vol 2 (1) ◽  
pp. 38-49
Author(s):  
Lakhdar Benhamed ◽  
Sidi Mohamed Mekelleche ◽  
Wafaa Benchouk
Keyword(s):  
Lewis Acids ◽  
Major Product ◽  
Diels Alder ◽  
Unsaturated Ketone ◽  
Unsaturated Aldehydes ◽  
Aldehydes And Ketones ◽  
Theoretical Insight ◽  
Insight Into ◽  
Good Agreement

Experimentally, a reversal of chemoselectivity has been observed in catalyzed Diels–Alder reactions of α,β-unsaturated aldehydes (e.g., (2E)-but-2-enal) and ketones (e.g., 2-hexen-4-one) with cyclopentadiene. Indeed, using the triflimidic Brønsted acid Tf2NH as catalyst, the reaction gave a Diels–Alder adduct derived from α,β-unsaturated ketone as a major product. On the other hand, the use of tris(pentafluorophenyl)borane B(C6F5)3 bulky Lewis acid as catalyst gave mainly the cycloadduct of α,β-unsaturated aldehyde as a major product. Our aim in the present work is to put in evidence the role of the catalyst in the reversal of the chemoselectivity of the catalyzed Diels–Alder reactions of (2E)-but-2-enal and 2-Hexen-4-one with cyclopentadiene. The calculations were performed at the ωB97XD/6-311G(d,p) level of theory and the solvent effects of dichloromethane were taken into account using the PCM solvation model. The obtained results are in good agreement with experimental outcomes.

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