Synthesis of aromatic heterocycles

Gilchrist, T. L.

doi:10.1039/a904578c

Cited by 221 publications

(65 citation statements)

References 629 publications

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“…[3] Consequently, great efforts have been made to find efficient synthetic methodologies to gain access to pyrroles. [4] While many new synthetic ap-A C H T U N G T R E N N U N G proches toward the pyrrole skeleton have been established in recent years, [5] it is still highly desirable to develop simple, convenient methods for the synthesis of polysubstituted pyrroles. Herein we wish to report a new protocol for the synthesis of polysubstituted pyrroles which employs the coupling reactions between phenyliodonium ylides and enamine esters.…”

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confidence: 99%

The Synthesis of Polysubstituted Pyrroles via the Coupling of Phenyliodonium Ylides and Enamine Esters

Wang

et al. 2009

Adv Synth Catal

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Abstract:The boron trifluoride etherate A C H T U N G T R E N N U N G (BF 3 ·Et 2 O)-catalyzed reactions between phenyliodonium ylides and enamine esters provide an efficient method for the synthesis of polysubstituted pyrroles.Keywords: coupling reactions; enamine esters; phenyliodonium ylides; pyrroles Pyrroles constitute an important category of heterocyclic ring systems which exist in many naturally occurring products.[1] Many pyrrole-containing compounds exhibit important biological and pharmaceutical activities, [2] and are found to be of great utility in materials sciences.[3] Consequently, great efforts have been made to find efficient synthetic methodologies to gain access to pyrroles.[4] While many new synthetic ap-A C H T U N G T R E N N U N G proches toward the pyrrole skeleton have been established in recent years, [5] it is still highly desirable to develop simple, convenient methods for the synthesis of polysubstituted pyrroles. Herein we wish to report a new protocol for the synthesis of polysubstituted pyrroles which employs the coupling reactions between phenyliodonium ylides and enamine esters.Phenyliodonium ylides derived from 1,3-dicarbonyl compounds are useful synthetic imtermediates which have aroused much attention during the last decade. [6] Phenyliodonium ylides can be transformed to carbenoids by the catalysis of transitional metals such as copper(I) and Rh(II), and subsequently undergo C À H insertion or addition to alkenes. [7] On the other hand, the reactions of phenyliodonium ylides under metalfree conditions are far less explored. It was reported recently that phenyliodonium ylides could be coupled with electron-rich arenes in the presence of Lewis acids.[8] Considering the electrophilic character of iodonium ylides, we envisioned that by using acids as catalyst, electron-rich olefins such as enamine esters might also react with iodonium ylides, giving rise to coupling product A, which could undergo further reactions to form pyrroles (Scheme 1). As both enamine esters and phenyliodonium ylides can be easily accessed from simple starting materials, it was expected that this strategy, if successful, would constitute a convenient approach for the synthesis of polysubstituted pyrroles.To achieve this goal, firstly the reaction conditions were explored using iodonium ylide 1a and enamine ester 2a as the substrates, and the reaction was performed in CH 2 Cl 2 . To our delight, we found that, with several commonly used acids as the catalysts, the pyrrole product 3aa was formed just as expected (Table 1). The best result was obtained when BF 3 ·Et 2 O was used (Table 1, entry 2). The reaction was complete in just 10 min, and the yield of 3aa reached 96%. By comparison, the reaction did not COMMUNICATIONS take place in the absence of catalyst (Table 1, entry 1). Further experiments showed that the reaction proceeded well in several solvents, among which CH 2 Cl 2 and acetonitrile led to the best results (Table 2). It is interesting to see that copper(I) salts could also catalyze the reactio...

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The Synthesis of Polysubstituted Pyrroles via the Coupling of Phenyliodonium Ylides and Enamine Esters

Wang

et al. 2009

Adv Synth Catal

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“…Refluxing of 6 with sodium azide in DMF in the presence of few drops of H 2 SO 4 afforded 5,7-dimethyl-2H-pyrido[3,2-e] [1,3]thiazin-4(3H)-one (7) (Scheme 1). The IR spectrum of 7 showed absorption band at 1684 cm À1 corresponding to amide carbonyl group, whereas its 1 H NMR spectrum revealed the presence of singlet signal at d 3.33 ppm because of methylene protons of thiazine ring and a signal at d 13.8 ppm because of NH proton.…”

Section: Resultsmentioning

confidence: 99%

“…Fused heterocycles containing sulfur such as thienopyridine, pyridothiazine, and some related fused heterocycles as new ring systems were achieved. Bicyclic thienopyridine 6 and pyrido [3,2-e] [1,3]thiazin-4(3H)-one 7 exhibited good antitumor activities compared with 5-fluorouracil.…”

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Utilization of 2‐Chloronicotinonitrile in the Syntheses of Novel Fused Bicyclic and Polynuclear Heterocycles of Anticipated Antitumor Activity

Hamama

Waly

EL-Hawary

et al. 2016

Journal of Heterocyclic Chem

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Some of synthetic bicyclic and polynuclear heterocyclic compounds based on pyridine scaffold were tested as in vitro antitumor agents, and these compounds found to exhibit interesting activities. Fused heterocycles containing sulfur such as thienopyridine, pyridothiazine, and some related fused heterocycles as new ring systems were achieved. Bicyclic thienopyridine 6 and pyrido[3,2‐e][1,3]thiazin‐4(3H)‐one 7 exhibited good antitumor activities compared with 5‐fluorouracil.

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“…[5,6] Most syntheses rely on classical condensation reactions of carbonyl compounds or thermal and metal-catalysed cycloadditions [7] but they are often restricted in terms of functional group tolerability. [8] Chirality is commonly introduced in a subsequent enantioselective transformation or by any type of chiral resolution. Incorporation of non-racemic chiral starting materials provides another convenient route for the synthesis of pyridines with stereogenic centres.…”

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Highly Functionalised Enantiopure 4‐Hydroxypyridine Derivatives by a Versatile Three‐Component Synthesis

Eidamshaus

Reißig

2009

Adv Synth Catal

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Synthesis of aromatic heterocycles

Cited by 221 publications

References 629 publications

The Synthesis of Polysubstituted Pyrroles via the Coupling of Phenyliodonium Ylides and Enamine Esters

The Synthesis of Polysubstituted Pyrroles via the Coupling of Phenyliodonium Ylides and Enamine Esters

Utilization of 2‐Chloronicotinonitrile in the Syntheses of Novel Fused Bicyclic and Polynuclear Heterocycles of Anticipated Antitumor Activity

Highly Functionalised Enantiopure 4‐Hydroxypyridine Derivatives by a Versatile Three‐Component Synthesis

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