The Reversibility of Aromatic Mercuration

Malaiyandi, M.; Sawatzky, H; Wright, Gillian

doi:10.1139/v61-240

Cited by 17 publications

(6 citation statements)

References 2 publications

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“…The reaction mixture was quenched in aqueous sodium chloride, and the solution was evaporated under reduced pressure until a white solid remained. The bromination of arylthallium chlorides was performed with bromine in carbon tetrachloride according to the procedure described by Wright (13). Product bromoarenes were analyzed by gas/liquid chromatography as in the case of mercuration.…”

Section: Methodsmentioning

confidence: 99%

Electrophilic mercuration and thallation of benzene and substituted benzenes in trifluoroacetic acid solution

Oláh

Hashimoto

Lin

1977

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

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The mercuration and thallation of benzene and substituted benzenes was studied with mercuric and thallic trifluoroacetate, respectively, in trifluoroacetic acid. With the shortest reaction time (1 sec) at 00, the relative rate of mercuration of toluene compared to that of benzene was 17.5, with the isomer distribution in toluene of: ortho, 17.4%; meta, 5.9%; and para, 76.7%. The isomer distribution in toluene varied with the reaction time, significantly more at 25°than at 00. The competitive thallation of benzene and toluene with thallic trifluoroacetate in trifluoroacetic acid at 150 showed the relative rate, toluene/benzene, to be 33, with the isomer distribution in toluene of: ortho, 9.5%; meta, 5.5%; and para, 85.0%. With increasingly higher reaction temperatures in both mercuration and thallation reactions of aromatics, isomerization (both intramolecular and intermolecular) within the relevant ortho-and para-metallated intermediate ions and/or of the isomers becomes more important. Competitive rates and isomer distributions of mercuration and thallation of benzene and substituted benzenes were also determined. The predominant para substitution in both mercuration and thallation of methylbenzenes reflects, besides some steric factors, the strong stabilizing effect of para methyl groups on the arenium ion intermediates. Under predominantly kinetically controlled conditions, no anomalous increase in the amount of meta substitution was observed.The mercuration of aromatic hydrocarbons with mercuric trifluoroacetate in trifluoroacetic acid at 250 has been studied, predominantly by Brown and coworkers (1-3). The rate ratio of toluene to benzene (kT/kB) was found to be 9.89 and the isomer distribution in toluene was: ortho, 12.2%; meta, 8.6%; and para, 79.2%. From these results, as well as from their preceding studies in acetic acid solution with perchloric acid catalyst giving kT/kB = 3.6-7, and 12-16% meta isomer, it was concluded that the relatively high meta isomer ratio observed was due to the high electrophilic reactivity of the mercurating agent causing the observed low selectivity substitutions. These results were correlated by the so-called Brown selectivity relationship (for a review, see ref. 4).It should be pointed out that, in their original paper on mercuration of toluene and benzene, Brown and Nelson, (5) extending the claimed quantitative selectivity relationship governing isomer distributions in aromatic substitution, commented on the preceding work of Klapproth and Westheimer (6) who found that, in glacial acetic acid with perchloric acid as catalyst, toluene was mercurated by mercuric acetate at 250 to give 6% of the meta isomer. Brown and Nelson claimed to have observed 12% meta isomer under similar conditions and stated "we are, however, unable to account for the differences between the values of the meta isomer." In the former case (6), a precise radiochemical technique was used in establishing orientation, whereas infrared analysis was utilized in the latter. iments at 250 and quenc...

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Section: Methodsmentioning

confidence: 99%

Electrophilic mercuration and thallation of benzene and substituted benzenes in trifluoroacetic acid solution

Oláh

Hashimoto

Lin

1977

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

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“…Although the synthesis and applications of polymetalated derivatives of benzene (C 6 R 6− n M n , n = 3−6) are well-documented, most of them involve representative elements. The element best studied is Hg(II), for which examples with three, four, − five, ,, and six metal atoms around a benzene ring have been reported. Hexalithiobenzene has also been described and shown to possess excellent thermodynamic stability .…”

Section: Introductionmentioning

confidence: 99%

Synthesis of Mono-, Di-, and Tripalladated 1,3,5-Benzenetricarboxaldehyde Complexes

et al. 2009

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The oxidative addition of 2,4,6-tribromo-1,3,5-benzenetricarboxaldehyde (C6(CHO)3Br3) to 1, 2, or 3 equiv of [Pd(dba)2] ([Pd2(dba)3]·dba) and N∧N affords, respectively, the mono-, di-, or trinuclear complexes [Pd{C6(CHO)3Br2}Br(N∧N)] (N∧N = tmeda = N,N,N′,N′-tetramethylethylenediamine (1a), tbbpy = 4,4′-di-tert-butyl-2,2′-bipyridine (1b), bpy = 2,2′-bipyridine, (1c)); [{PdBr(N∧N)}2{μ2-C6(CHO)3Br}] (N∧N = tmeda (2a), tbbpy (2b)); or [{PdBr(N∧N)}3{μ3-C6(CHO)3}] (N∧N = tmeda (3a), tbbpy (3b)). The reactions of C6(CHO)3Br3 with a mixture of [Pd(dba)2] and PR3 lead, depending on the nature of the phosphine and the molar ratio of the reagents, to the mononuclear trans-[Pd{C6(CHO)3Br2}Br(PR3)2] (R = Ph (1d), R3 = Me2Ph (1e)) or the dinuclear [{trans-PdBr(PMe2Ph)2}2{μ2-C6(CHO)3Br}] (2e) complex. All attempts to prepare trinuclear phosphine complexes using this method of synthesis have been unsuccessful. However, displacement of the tbbpy ligand in 3b by an excess of PMe3 affords the trinuclear complex [{trans-PdBr(PMe3)2}3{μ3-C6(CHO)3}] (3f). The crystal structures of 1b, 1d, 2a·CDCl3, and 2e have been determined by X-ray diffraction studies.

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“…The element best studied is Hg(II), of which compounds with three to six metal atoms have been reported. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17] Other members of this family of com-pounds include Sn(IV), 1,3,18-21 Li, 1,3,22-26 Mg, 3 Al, 27,28 and Ge derivatives. 29,30 Many Hg(II) derivatives were prepared by metalation, but in a few cases transmetalation reactions using the corresponding Sn(IV) 1 or Li 3 derivatives were used.…”

Section: Introductionmentioning

confidence: 99%

Polymetalated Aromatic Compounds. 1. Synthesis of Mono-, Di-, and Tripalladated Mesitylene Derivatives

et al. 2001

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The reaction of 1,3,5-triiodomesitylene (C 6 Me 3 I 3 ) with a mixture of [Pd(dba) 2 ] and PR 3 leads to the mononuclear complexes trans-[Pd(C 6 Me 3 I 2 )I(PR 3 ) 2 ] (R ) Ph (1), R 3 ) Me 2 Ph (2)) or the dinuclear complex [{trans-PdI(PMe 2 Ph) 2 } 2 (µ 2 -C 6 Me 3 I)] (3), depending on the nature of the phosphine, the temperature, and the molar ratio of the reagents. All attempts to prepare trinuclear complexes, using this method of synthesis, were unsuccessful. However, addition of C 6 Me 3 I 3 to a mixture of [Pd(dba) 2 ] and L 2 gives at room temperature [(PdIL 2 ) 3 -(µ 3 -C 6 Me 3 )] (L 2 ) 2,2′-bipyridine (bpy) (4), 4,4′-di-tert-butyl-2,2′-bipiridine (tbbpy) (5)), even if substoichiometric amounts of Pd were used. Complex 5 does not react with PPh 3 or PMe 2 -Ph, but it does react with PMe 3 to give [trans-{PdI(PMe 3 ) 2 } 3 (µ 3 -C 6 Me 3 )] (6). The crystal structures of 1, 2, and 5 have been determined by X-ray diffraction studies.

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The Reversibility of Aromatic Mercuration

Cited by 17 publications

References 2 publications

Electrophilic mercuration and thallation of benzene and substituted benzenes in trifluoroacetic acid solution

Electrophilic mercuration and thallation of benzene and substituted benzenes in trifluoroacetic acid solution

Synthesis of Mono-, Di-, and Tripalladated 1,3,5-Benzenetricarboxaldehyde Complexes

Polymetalated Aromatic Compounds. 1. Synthesis of Mono-, Di-, and Tripalladated Mesitylene Derivatives

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