Sterically hindered aromatic compounds. IX. Electron spin resonance and product studies of the dediazoniation reaction

Barclay, L. R. C.; Briggs, Alexander G.; Briggs, W. E.; Dust, Julian M.; Gray, J. A.

doi:10.1139/v79-348

Cited by 11 publications

(5 citation statements)

References 10 publications

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“…This is a somewhat specialized system and our conclusions cannot readily be generalized. Nevertheless, the fact that radicals are trapped while at the same time products form from ionic pathways, in these and earlier (13) studies, indicates that ionic and radical reactions are independently occurring as shown in simplified form in Scheme 3. More detailed arguments in favour of a similar scheme have been given by Bunnett and co-workers (38).…”

Section: C! -Ch (4)supporting

confidence: 59%

“…N-Nitroso-2,4,6-tri-tert-butylacetanilide (1) was prepared as described (13) and purified by preparative tlc immediately before use. N-Nitrosoacetanilide was prepared as described (39) and stored at -20°C over potassium hydroxide pellets.…”

Section: Materi~zls Atzd T7zethodsmentioning

confidence: 99%

“…The nmr measurements were made with a Varian EM360-L spectrometer and ir spectra were determined on a Perkin-Elmer 467 spectrometer. Electron spin resonance spectra were recorded on a Varian E-3 spectrometer using an esr reactor tube as previously described (13) and theg values measured relative to that of tetracene in sulfuric acid, g = 2.002604 (41). Melting points were determined on a hot stage and are uncorrected.…”

Section: Materi~zls Atzd T7zethodsmentioning

confidence: 99%

“…The products were identified, where applicable (e.g. hydrocarbons 5 and 6, 2,4,6-tri-tert-butylacetanilide, 2-(3,s-di-tert-butylpheny1)-2-methylpropanal oxime 13), by comparison of their nmr and ir spectra and melting points with those previously found (13,17). 2,4,6-Tri-tert-butylphenyl acetate (3), the major product from 1 in benzene, gave mp 100-102°C (lit.…”

Section: Materi~zls Atzd T7zethodsmentioning

confidence: 99%

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Sterically hindered aromatic compounds. XI. Spectral and product studies of the decomposition of N-nitrosoacetanilides

Barclay¹,

Dust²

1982

Can. J. Chem.

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DUST. Can. J. Chem. 60,607 (1982). Decomposition of N-nitroso-2,4,6-tri-?err-butylacetanilide (1) in benzene forms products 2,4,6-tri-rert-butylphenyl acetate ( 3 , 3-(3,5-di-tert-butyIphenyl)-2-acetoxy-2-methypropane (4), and hydrocarbons 3-(3,s-di-terr-butylpheny1)-and I-(3,5-di-terr-butylphenyl)-2-methylpropene (5 and 6) explained by a reactive aryl cation (21, the rearranged products (4, 5, 6) originating from a 1,5-hydride shift from an ortho tert-butyl group in 2. In contrast, decomposition of 1 in triethylamine forms products 1,3,5-tri-rerr-butylbenzene (lo), 2,4,6-tri-tert-butylacetanilide (151, and 2-(3,5-di-terr-butylpheny1)-2-methylpropan oxime (13), expected of a free radical pathway. Electron spin resonance evidence is given for intermediates formed by rearrangement of the 2,4,6-tri-tert-butylphenyl radical and spin trapped by the nitroso group of 1. CIDNP and esr studies on the dediazoniation of N-nitrosoacetanilide and aniline in the presence of tertiary amines support the proposed electron transfer mechanism. The results are briefly discussed in terms of the role of steric effects and electron transfer in the dediazoniation of nitrosoacetanilides and diazonium salts.L. Ross C. BARCLAY et JULIAN M. DUST. Can. J. Chem. 60,607 (1982). La decomposition du N-nitroso tri-tert-butyl-2,4,6 acetanilide (1) dans le benzene conduit a la formation de I'acttate de tri-rert-butyl-2,4,6 phenyle (3), de (di-tert-butyl-3,5 phenyl)-3 acetoxy-2 methyl-2 propane (4) et des (di-terr-butyl-3,5 phCny1)-3 et (di-tert-butyl-3,5 ph6nyl)-1 methyl-2 propenes (5 et 6) dont on explique la formation a I'aide d'un cation aryle reactif (2), les produits de transposition ( 4 , s et 6) proviennent d'un deplacement-1,5 d'un hydmre provenant d'un groupement tert-butyle ortho dans 2. Par opposition, la decomposition de 1 dans la triethylamine conduit a la formation de tri-tert-butyl-1,3,5 benzene (lo), de tri-terr-butyl-2,4,6 acetanilide (15) et de l'oxime du (di-tert-butyl-3,5 phenyl)-2 methyl-2 propanal (13) dont la formation est prevue pour un processus radicalaire. Les donnees de la rpe suggerent la presence d'intermediaires formes par une transposition du radical tri-tert-butyl-2,4,6 phenyle qui est piege par le nitroso de 1. Des etudes de CIDNP et rpe sur la dediazotation du N-nitrosoacetanilide et de I'aniline en presence d'amines tertiaires est en accord avec le mecanisme de transfert d'electron propose. On discute brievement des resultats obtenus en termes du r81e des effets steriques et des transferts d'electrons lors de la dediazotation des nitrosoacetanilides et des sels de diazonium.[Traduit par le journal]

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Section: C! -Ch (4)supporting

confidence: 59%

Section: Materi~zls Atzd T7zethodsmentioning

confidence: 99%

Section: Materi~zls Atzd T7zethodsmentioning

confidence: 99%

Section: Materi~zls Atzd T7zethodsmentioning

confidence: 99%

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Sterically hindered aromatic compounds. XI. Spectral and product studies of the decomposition of N-nitrosoacetanilides

Barclay¹,

Dust²

1982

Can. J. Chem.

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“…The special nature of molecule 37 is seen when primary radical 44 abstracts a bromine atom from isopropyl analogue 43; here, in the absence of bulky tert-butyl groups, the reaction is significantly endergonic. 33 Hydrocarbon 28 arises from radical 29 by intramolecular 1,4-HAT via quantum mechanical tunneling, followed by neophyl rearrangement of primary alkyl radical 30 32,35 to the more stabilized tertiary radical 32 as a thermodynamic sink (supported by computation, see Supporting Information). Besides isolation of 28, further evidence for radical 32 as an intermediate came from detection of its dimer by GC−MS (see Supporting Information), 36 although this dimer was not produced in sufficient quantities for isolation.…”

Section: Journal Of the American Chemical Societymentioning

confidence: 97%

Dual Roles for Potassium Hydride in Haloarene Reduction: CS_NAr and Single Electron Transfer Reduction via Organic Electron Donors Formed in Benzene

et al. 2018

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Potassium hydride behaves uniquely and differently than sodium hydride toward aryl halides. Its reactions with a range of haloarenes, including designed 2,6-dialkylhaloarenes, were studied in THF and in benzene. In THF, evidence supports concerted nucleophilic aromatic substitution, CS N Ar, and the mechanism originally proposed by Pierre et al. is now validated through DFT studies. In benzene, besides this pathway, strong evidence for single electron transfer chemistry is reported. Experimental observations and DFT studies lead us to propose organic super electron donor generation to initiate BHAS (base-promoted homolytic aromatic substitution) cycles. Organic donor formation originates from deprotonation of benzene by KH; attack on benzene by the resulting phenylpotassium generates phenylcyclohexadienylpotassium that can undergo (i) deprotonation to form an organic super electron donor or (ii) hydride loss to afford biphenyl. Until now, BHAS reactions have been triggered by reaction of a base, MOtBu (M = K, Na), with many different types of organic additive, all containing heteroatoms (N or O or S) that enhance their acidity and place them within range of MOtBu as a base. This paper shows that with the stronger base, KH, even a hydrocarbon (benzene) can be converted into an electron-donating initiator.

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Zur Chemie des (2,4,6‐Tri‐tert‐butylphenyl)isocyanids

Pakusch

Rüchardt

1989

Chem. Ber.

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Oa the Chemistry of (2,4,6-Tri-m-butylpaensr)isocyPnide The thermal rearrangement of (2,4,6-tri-tert-butylphenyl)isocyanide, available from 1,3,5-tri-tert-butylbenzene in 45% yield by a four-step synthesis, offers a high-yield access to 2,4,6-tritert-butylbenzonitrile and -benzoic acid The rate of this rearrangement is only slightly retarded by the bulky ortho substituentg confirming the pericyclic transition state proposed earlier. Synthetische Arbeiten2,4,6-Tri-tert-butyIbenzonitril und die korrespondierende Benzoesaure sind Verbindungen, die bisher schwer zuganglich aber von theoretischem Interesse sind4). Insbesondere die Synthese durch Sandmeyer-Reaktion rnit 2,4,6-Tri-tert-butylanilin gelingt aufgrund der Instabilitat des entsprechenden Diazonium-Ions 3a,5a) nicht in

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Sterically hindered aromatic compounds. IX. Electron spin resonance and product studies of the dediazoniation reaction

Cited by 11 publications

References 10 publications

Sterically hindered aromatic compounds. XI. Spectral and product studies of the decomposition of N-nitrosoacetanilides

Sterically hindered aromatic compounds. XI. Spectral and product studies of the decomposition of N-nitrosoacetanilides

Dual Roles for Potassium Hydride in Haloarene Reduction: CS_NAr and Single Electron Transfer Reduction via Organic Electron Donors Formed in Benzene

Zur Chemie des (2,4,6‐Tri‐tert‐butylphenyl)isocyanids

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Sterically hindered aromatic compounds. IX. Electron spin resonance and product studies of the dediazoniation reaction

Cited by 11 publications

References 10 publications

Sterically hindered aromatic compounds. XI. Spectral and product studies of the decomposition of N-nitrosoacetanilides

Sterically hindered aromatic compounds. XI. Spectral and product studies of the decomposition of N-nitrosoacetanilides

Dual Roles for Potassium Hydride in Haloarene Reduction: CSNAr and Single Electron Transfer Reduction via Organic Electron Donors Formed in Benzene

Zur Chemie des (2,4,6‐Tri‐tert‐butylphenyl)isocyanids

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Dual Roles for Potassium Hydride in Haloarene Reduction: CS_NAr and Single Electron Transfer Reduction via Organic Electron Donors Formed in Benzene