Intramolecular Aromatic Substitution With Bisthiocarbocations. Variations of Lewis Acid, Solvent and Orthothio Substituents

1990 ◽  
Vol 43 (5) ◽  
pp. 815 ◽  
Author(s):  
SA Gamage ◽  
SA Gamage ◽  
RAJ Smith ◽  
RAJ Smith
Keyword(s):  
Lewis Acid ◽  
Electrophilic Aromatic Substitution ◽  
Aromatic Substitution

The effects of Lewis acid, solvent and orthothio substituent have been examined with regard to intramolecular electrophilic aromatic substitution ( annulation ) with bisthiocarbocations . A suspension of silver trifluoromethanesulfonate in dichloromethane, creating bis ( arylthio ) carbocations, was found to be the most effective for annulation of six- membered rings.

Efficient construction of benzohydrindenones from aryltrienones via domino Nazarov electrocyclization – electrophilic aromatic substitution

2004 ◽  
Vol 82 (2) ◽  
pp. 375-385 ◽  
Author(s):  
Cindy C Browder ◽  
Fredrik P Marmsäter ◽  
F G West
Keyword(s):  
Low Temperature ◽  
Lewis Acid ◽  
Quantitative Yield ◽  
Electrophilic Aromatic Substitution ◽  
Side Chains ◽  
Aromatic Substitution ◽  
Nazarov Cyclization ◽  
Efficient Construction

1,4-Dien-3-ones substituted with pendant arylethyl side chains attached at C-1 were readily prepared from substituted dihydrocinnamaldehydes. Treatment with TiCl4 at low temperature effected domino Nazarov electrocyclization – arene trapping within 5 min to give racemic benzohydrindenones in near-quantitative yield and with complete diastereoselectivity.Key words: domino process, electrophilic aromatic substitution, Lewis acid, Nazarov cyclization.

Synthesis of Bench-Stable N-Quaternized Ketene N,O-Acetals and Preliminary Evaluation as Reagents in Organic Synthesis

2019 ◽  
Author(s):  
Alisha M. Blades ◽  
Danielle L. McConnell ◽  
Danielle Gomes Rodrigues ◽  
Phoebe V. Keyes ◽  
Justin C. Sonberg ◽  
...  
Keyword(s):  
Organic Synthesis ◽  
Lewis Acid ◽  
Reactive Intermediates ◽  
Electrophilic Aromatic Substitution ◽  
Preliminary Evaluation ◽  
Aromatic Substitution ◽  
Triflic Acid ◽  
Synthetic Intermediates ◽  
Nucleophilic Aromatic Substitutions

<div>N-Quaternized ketene N,O-acetals are typically an unstable, transient class of compounds most commonly observed as reactive intermediates. In this report, we describe a general approach to a variety of benchstable N-quaternized ketene N,O-acetals via treatment of pyridine or aniline bases with ethoxyacetylene and an appropriate Brønsted or Lewis acid (triflic acid, triflimide, or scandium(III) triflate). The resulting pyridinium and anilinium salts may be used as reagents or synthetic intermediates in multiple reaction types. For example, N-(1-ethoxyvinyl) pyridinium or anilinium salts can thermally release highly reactive O-ethyl ketenium ions that undergo electrophilic aromatic substitution with electron rich arenes. N-(1-ethoxyvinyl)-2-halopyridinium salts can also be utilized in peptide couplings as a derivative of Mukaiyama reagents, or react with alcohol and amines in nucleophilic aromatic substitutions.</div>

AlCl3-Catalyzed Intramolecular Hydroarylation of Arenes with Alkynes

Synlett ◽  
2017 ◽  
Vol 28 (16) ◽  
pp. 2159-2162 ◽  
Author(s):  
Guangxin Gu ◽  
Hao Guo ◽  
Yang Li ◽  
Yu Wang ◽  
Dawen Xu ◽  
...  
Keyword(s):  
Reaction Mechanism ◽  
Lewis Acid ◽  
Substitution Reaction ◽  
Functional Group ◽  
Catalytic Amount ◽  
Main Group ◽  
Electrophilic Aromatic Substitution ◽  
Aromatic Substitution ◽  
Main Group Metal ◽  
Acid Catalyzed

Herein, we wish to report the main-group metal Lewis acid catalyzed intramolecular hydroarylation of arenes with alkynes. This cyclization proceeds efficiently in the presence of a catalytic amount of AlCl3, affording phenanthrenes in moderate to excellent yields. The catalyst is cheap and nontoxic. The functional-group tolerance is high. A plausible electrophilic aromatic substitution reaction mechanism is proposed for this transformation.

scholarly journals Synthesis of Bench-Stable N-Quaternized Ketene N,O-Acetals and Preliminary Evaluation as Reagents in Organic Synthesis

2019 ◽  
Author(s):  
Alisha M. Blades ◽  
Danielle L. McConnell ◽  
Danielle Gomes Rodrigues ◽  
Phoebe V. Keyes ◽  
Justin C. Sonberg ◽  
...  
Keyword(s):  
Organic Synthesis ◽  
Lewis Acid ◽  
Reactive Intermediates ◽  
Electrophilic Aromatic Substitution ◽  
Preliminary Evaluation ◽  
Aromatic Substitution ◽  
Triflic Acid ◽  
Synthetic Intermediates ◽  
Nucleophilic Aromatic Substitutions

<div>N-Quaternized ketene N,O-acetals are typically an unstable, transient class of compounds most commonly observed as reactive intermediates. In this report, we describe a general approach to a variety of benchstable N-quaternized ketene N,O-acetals via treatment of pyridine or aniline bases with ethoxyacetylene and an appropriate Brønsted or Lewis acid (triflic acid, triflimide, or scandium(III) triflate). The resulting pyridinium and anilinium salts may be used as reagents or synthetic intermediates in multiple reaction types. For example, N-(1-ethoxyvinyl) pyridinium or anilinium salts can thermally release highly reactive O-ethyl ketenium ions that undergo electrophilic aromatic substitution with electron rich arenes. N-(1-ethoxyvinyl)-2-halopyridinium salts can also be utilized in peptide couplings as a derivative of Mukaiyama reagents, or react with alcohol and amines in nucleophilic aromatic substitutions.</div>

The electrophilic aromatic substitution approach to C–H silylation and C–H borylation

2018 ◽  
Vol 90 (4) ◽  
pp. 723-731 ◽  
Author(s):  
Susanne Bähr ◽  
Martin Oestreich
Keyword(s):  
Transition Metal ◽  
Lewis Acid ◽  
Electrophilic Aromatic Substitution ◽  
Bronsted Acid ◽  
Aromatic Substitution ◽  
Brønsted Acid ◽  
Brönsted Acid ◽  
Transition Metal Catalyzed ◽  
Metal Catalyzed

AbstractSeveral approaches toward electrophilic C–H silylation of electron-rich arenes are discussed, comprising transition-metal-catalyzed processes as well as Lewis-acid- and Brønsted-acid-induced protocols. These methods differ in the catalytic generation of the silicon electrophile but share proton removal in form of dihydrogen. With slight modifications, these methods are often also applicable to the related electrophilic C–H borylation.

EFFECT OF LEWIS ACID CATALYSTS ON THE POSITIONAL SELECTIVITY OF THE ELECTROPHILIC AROMATIC SUBSTITUTION ON α-SUBSTITUTED THIOPHENES: A CONCEPTUAL DFT INVESTIGATION

2011 ◽  
Vol 10 (04) ◽  
pp. 435-445
Author(s):  
AMINA GHOMRI ◽  
SIDI MOHAMED MEKELLECHE
Keyword(s):  
Quantum Chemistry ◽  
Lewis Acid ◽  
Electrophilic Aromatic Substitution ◽  
Acid Catalysts ◽  
Aromatic Substitution ◽  
Lewis Acid Catalysts ◽  
Reactivity Indices ◽  
Quantum Chemistry Calculations ◽  
Theoretical Results ◽  
Good Agreement

The α′/β regioselectivity of the electrophilic aromatic substitution of some thiophene α-substituted derivatives ( R = CHO, COMe or CO2Me ), catalyzed and not catalyzed by the Lewis acid, AlCl3 , has been investigated by means of the local nucleophilicity index, recently proposed by Pérez et al. [J Mol Struct: Theochem895: 86, 2009]. The quantum chemistry calculations, carried out at the B3LYP/6-311G(d,p) level of theory, show that the α′-substitution is preferred in absence of the catalyst, while the β-substitution is more favored in the presence of the catalyst. The theoretical results, predicted using DFT-based reactivity indices, are in good agreement with the experimental outcomes.

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