Formation of C60Ph12 by electrophilic aromatic substitution

Taylor, Roger; Langley, G. John; Meidine, Mohamed F.; Parsons, Jonathan P.; Abdul‐Sada, Alaa; Dennis, T. John S.; Hare, Jonathon; Kroto, Harold W.; Walton, D. R. M.

doi:10.1039/c39920000667

Cited by 67 publications

(57 citation statements)

References 8 publications

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“…13a,15,17,25 Accordingly, we drew our attention to mechanism D. Importantly, the absence of an isotope effect in the arylation of 1a, mentioned above (Scheme 4), does not contradict with electrophilic mechanism D. In this case, C-H cleavage is a fast step, 26 and thus no isotope effect could be expected. Furthermore, it is generally believed that the pyrrole ring of indolizines is rather electron-rich, as it easily undergoes electrophilic substitution reactions.…”

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confidence: 93%

Palladium-Catalyzed Arylation and Heteroarylation of Indolizines

et al. 2004

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A highly effective protocol for palladium-catalyzed selective arylation and heteroarylation of indolizines at C-3 has been developed. Mechanistic studies unambiguously support an electrophilic substitution pathway for this transformation.Indolizines substituted at C-3 are very attractive heterocyclic units, as a number of representatives of this class 1 and, especially their partially or completely reduced analogues, indolizidine alkaloids 2 and related unnatural compounds, 3 exhibit important biological properties. As a part of our program on developing efficient methods toward differently substituted indolizines, we were particularly interested in elaborating efficient approaches toward C-3-arylated indolizines. To date, no general convenient methods for synthesis of C-3-arylated indolizines exist. 4 Scattered reports on synthesis of C-3-arylated indolizines via various modes of Chichibabin-type cyclocondensation 5 are limited to particular substitution patterns 6 and generally provide low to moderate yields of the products. 7 Other methods such as dipolar cycloaddition of pyridinium ylides with alkynes, 8 cyclopropenones, 9 or cyclopropenes 10 are limited to use of symmetric substrates, producing indolizines with two identical substituents at the pyrrole ring. Finally, synthesis of indolizines via cycloisomerization of alkynyl pyridines, 11,12 a method recently developed within our group, potentially can give access to 3-arylindolizines; however, it would require employment of rather expensive 3-aryl-1-propynes and, in this case, is unlikely to be considered as synthetically useful. Thus, we decided to explore the possibility of direct, last-stage methods of arylation of the indolizine core. Although analogous reactions on various heterocyclic systems such as furans, 13 thiophenes, 13a,14 pyrroles, 15 and indoles 16 have long been known, no reports on arylations involving indolizines have been reported to date. 17 Herein we report efficient palladium-catalyzed arylation and heteroarylation of indolizines, which allows for selective incorporation of aromatic or heteroaromatic substituent at the C-3 position of this heterocycle.Initial experiments revealed that indolizine 1a indeed underwent arylation in the presence of different palladium sources in DMSO; however, a 3-fold excess with respect to arylbromide © 2004 American Chemical Society Correspondence to: Vladimir Gevorgyan, vlad@uic.edu. Supporting Information Available: Detailed experimental procedures for preparation of and spectroscopic data for compounds 3aa-ed and 10. This material is available free of charge via the Internet at http://pubs.acs.org. NIH Public Access Author ManuscriptOrg Lett. Author manuscript; available in PMC 2013 July 11. NIH-PA Author ManuscriptNIH-PA Author Manuscript NIH-PA Author Manuscript was required to attain high yields, and the reaction was rather sluggish, as it took 2 days for completion. Optimization experiments 18 indicated that arylation of indolizines proceeded much faster (1-3 h) in the presence of cataly...

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Palladium-Catalyzed Arylation and Heteroarylation of Indolizines

et al. 2004

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“…Electrophilic substitution, considered to be the most characteristic reaction of aromatic systems, is typically described in textbooks, monographs, and reviews by the two-stage S E Ar mechanism depicted in Fig. 1 (5)(6)(7)(8)(9)(10)(11). Arenium ion (σ-complex) intermediates are often ascribed to Wheland (9) inaccurately, since Pfeiffer and Wizinger (10) laid out the principles of such species for bromination in 1928.…”

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Arenium ions are not obligatory intermediates in electrophilic aromatic substitution

Galabov

Koleva

Hadjieva

et al. 2014

Proc. Natl. Acad. Sci. U.S.A.

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Our computational and experimental investigation of the reaction of anisole with Cl 2 in nonpolar CCl 4 solution challenges two fundamental tenets of the traditional S E Ar (arenium ion) mechanism of aromatic electrophilic substitution. Instead of this direct substitution process, the alternative addition-elimination (AE) pathway is favored energetically. This AE mechanism rationalizes the preferred ortho and para substitution orientation of anisole easily. Moreover, neither the S E Ar nor the AE mechanisms involve the formation of a σ-complex (Wheland-type) intermediate in the rate-controlling stage. Contrary to the conventional interpretations, the substitution (S E Ar) mechanism proceeds concertedly via a single transition state. Experimental NMR investigations of the anisole chlorination reaction course at various temperatures reveal the formation of tetrachloro addition by-products and thus support the computed addition-elimination mechanism of anisole chlorination in nonpolar media. The important autocatalytic effect of the HCl reaction product was confirmed by spectroscopic (UV-visible) investigations and by HCl-augmented computational modeling.organic chemistry | reaction mechanisms | alternative computed routes | autocatalysis

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“…A plausible acylation mechanism that accounted for the cycliacylation of 24 and 25 is the generation of acyl carbocation 30 , either free or as an ion pair 31 which upon treatment with acidic catalysts losses water or alcohol. However, ring closures of 19 is explained to occur via an alkylation mechanism produce a primary carbocation.…”

Section: Resultsmentioning

confidence: 99%

Friedel-Crafts chemistry. Part 45: expedient new improved process for the synthesis of oxacarbazepine precursor 10,11-dihydro-10-oxo-5H-dibenz[b,f]azepine via Friedel-Crafts cycliacylations

El-Aal¹

2015

Arkivoc

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An unprecedented efficient methodology for the synthesis of 10,11-dihydro-10-oxo-5H-dibenz[b,f]azepine via a three new synthetic pathways is described. The key steps of this approach are based on classical Friedel-Craft ring closures of three precursors 1-(2-(N-phenyl-Ntosylamino)phenyl)-2-bromoethanone, ethyl 2-(2-(N-phenyl-N-tosylamino)phenyl)acetate or 2-(2-(N-phenyl-N-tosylamino)phenyl)acetic acid, by using AlCl 3 /CH 3 NO 2 or AlCl 3 in dichloromethane. For the latter two precursors, P 2 O 5 in toluene worked also well. The precursors were easily obtained in a two-or three -step reaction sequence. Overall, the described approach allows easy and efficient access to the tricyclic dibenzoazepinone ring system from easily accessible starting materials.

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Formation of C60Ph12 by electrophilic aromatic substitution

Abstract: A product of molecular formula C60Ph12 is obained by heating benzene, bromine and c60 in the presence of iron(iii) chloride; other phenylated and oxygenated derivatives are also present.

Cited by 67 publications

References 8 publications

Palladium-Catalyzed Arylation and Heteroarylation of Indolizines

Palladium-Catalyzed Arylation and Heteroarylation of Indolizines

Arenium ions are not obligatory intermediates in electrophilic aromatic substitution

Friedel-Crafts chemistry. Part 45: expedient new improved process for the synthesis of oxacarbazepine precursor 10,11-dihydro-10-oxo-5H-dibenz[b,f]azepine via Friedel-Crafts cycliacylations

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