The preparation and reactions of phenyl-substituted pyrylium and pyridinium salts: Nucleophilic substitution of an amino group by pyridine

Awartani, Radi; Sakizadeh, Kumars; Gabrielsen, Bjarne

doi:10.1021/ed063p172

Cited by 10 publications

(4 citation statements)

References 10 publications

(15 reference statements)

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“…A well‐known feature of TPP + is the presence of electrophilic sites, which are able to undergo nucleophilic attack on 2‐ and 6‐position of pyrylium ring . Considering vinyl ether as nucleophiles, the addition of these monomers onto TPP + is a relevant hypothesis.…”

Section: Resultsmentioning

confidence: 99%

Versatility of Pyrylium Salt/Vinyl Ether Initiating System for Epoxide Dual‐Cure Polymerization: Kick‐Starting Effect of the Coinitiator

Lecompère

Allonas

Maréchal

et al. 2017

Macromol. Rapid Commun.

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redox reaction mediated via radicals in depth, where the light does not penetrate anymore. In such case, the possible on-demand curing afforded by the photochemistry is an additional and attractive benefit. Indeed, these systems open new opportunities in industry where the cycle time becomes a more and more challenging task. In addition, the versatility of dual-cure initiating systems is intended to provide greater flexibility in the industrial processes.Recently, pyrylium salts have been reported as a new photothermal initiator for epoxide monomers under irradiation or by thermal heating. [15,16] In this paper, the versatility of pyrylium-based initiating systems combined with vinyl ethers as coinitiators is discussed. It is shown that 2,4,6-triphenylpyrylium tetrafluoroborate (TPP + ) behaves as a very effective cationic thermal initiator in the presence of small amounts of vinyl ether. Similarly, the photoinitiation ability of TPP + is slightly increased in the presence of vinyl ethers. These two features open the possibility to use this system as a dual-cure initiating system for cycloaliphatic epoxides. Moreover, a kickstarting effect is observed, which enables to tune the thermal reactivity of the initiating system. These results Pyrylium salts combined with vinyl ethers are shown to act as new versatile dual-cure initiating systems for both photochemical and thermal initiation of oxirane monomers. The combination of both possibilities allows the curing of thick samples through photoinduced frontal polymerization. On the basis of quantum calculations and photochemical experiments, some clues are given about the reaction mechanisms involved. Interestingly, a sequential kick-starting effect is observed in the presence of vinyl ether enabling the curing of oxetane monomers. Thereby, this communication presents a short overview of potential of pyrylium salts in cationic polymerization of oxiranes.

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Section: Resultsmentioning

confidence: 99%

Versatility of Pyrylium Salt/Vinyl Ether Initiating System for Epoxide Dual‐Cure Polymerization: Kick‐Starting Effect of the Coinitiator

Lecompère

Allonas

Maréchal

et al. 2017

Macromol. Rapid Commun.

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“…2,4,6-triphenylpyrylium tetrafluoroborate encountered in the literature [12] shows the signal of the pyrylium ring protons at δ H 8.50. These protons are more shielded than the styrylpyrylium perchlorate due certainly to the mesomeric effects.…”

Section: H Nmr Spectra Data Analysis H X or C Xmentioning

confidence: 88%

Styrylpyrylium Salts: and NMR High-Resolution Spectroscopy (1D and 2D)

Ouédraogo

Tapsoba

Sib

et al. 2010

International Journal of Spectroscopy

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and NMR high-resolution spectroscopy (1D and 2D) (, -COSY, HSQC, HMBC) for four styrylpyrylium perchlorates were carried out and signal attributions are reported. Chemical shifts observed on NMR spectra for the styrylpyrylium salts were compared with net atomic charge for carbon obtained by AM1 semiempirical calculations. The position of the styryl group present low effect on chemical shifts for carbon atoms, while the presence of methyl group led to the unshielding of the substituted carbon.

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“…As mentioned previously,t he Katritzky salts are formed via a simple ande fficient condensation reaction, which can also be carried out at room temperature in CH 2 Cl 2 ,i fa cetic acid is used as aB rønsted acid catalyst. [19] However,i ns ome cases isolation can be difficult if the Katritzky salt does not precipitate. Thus, we soughtt od evelop ao ne-pot procedure in which the Katritzky salt is generated and reactedi ns itu.…”

Section: Entrymentioning

confidence: 99%

Deaminative Borylation of Aliphatic Amines Enabled by Visible Light Excitation of an Electron Donor–Acceptor Complex

Sandfort

Strieth‐Kalthoff

Klauck

et al. 2018

Chemistry A European J

208

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A deaminative strategy for the borylation of aliphatic primary amines is described. Alkyl radicals derived from the single‐electron reduction of redox‐active pyridinium salts, which can be isolated or generated in situ, were borylated in a visible light‐mediated reaction with bis(catecholato)diboron. No catalyst or further additives were required. The key electron donor–acceptor complex was characterized in detail by both experimental and computational investigations. The synthetic potential of this mild protocol was demonstrated through the late‐stage functionalization of natural products and drug molecules.

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The preparation and reactions of phenyl-substituted pyrylium and pyridinium salts: Nucleophilic substitution of an amino group by pyridine

Abstract: This article makes a much needed contribution in the area of laboratory experiment for heterocyclic chemistry.

Cited by 10 publications

References 10 publications

Versatility of Pyrylium Salt/Vinyl Ether Initiating System for Epoxide Dual‐Cure Polymerization: Kick‐Starting Effect of the Coinitiator

Versatility of Pyrylium Salt/Vinyl Ether Initiating System for Epoxide Dual‐Cure Polymerization: Kick‐Starting Effect of the Coinitiator

Styrylpyrylium Salts: and NMR High-Resolution Spectroscopy (1D and 2D)

Deaminative Borylation of Aliphatic Amines Enabled by Visible Light Excitation of an Electron Donor–Acceptor Complex

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