Chemical polarisation of <sup>15</sup>N and <sup>13</sup>C nuclei in diazo coupling reactions

Lippmaa, É.; Pehk, Tõnis; Saluvere, T.; Mägi, Μ.

doi:10.1002/mrc.1270050911

Cited by 14 publications

(4 citation statements)

References 9 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Although the rather elusive aryl (step (viii)), although we cannot rule out oxygenation diazotate radical (i.e., 13 in Scheme 2) reported by of 12 by 13 followed by hydrogen abstraction or even Cadogan (28) was questioned on the basis of nuclear air oxidation of 12 during work-up (32). polarization studies (29), more recent evidence (30) 5. The esters 8 and 9 most probably form in com- tions to give this ester.…”

Section: Discussionmentioning

confidence: 89%

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

Barclay¹,

Briggs²,

Briggs³

et al. 1979

Can. J. Chem.

View full text Add to dashboard Cite

Can. J. Chem. 57,2 172 (1979). An esr study of the dediazoniation of 2,4,6-tri-tert-butylaniline with butyl nitrite in methylene chloride indicated the formation of the 2,4,6-tri-tert-butylphenyl radical which was spin trapped by the butyl nitrite. The persistent 2,4,6-tri-tert-butylphenoxy radical was also formed. Product studies from reactions catalyzed by pivalic acid indicate a novel rearrangement of an orthotert-butyl group under dediazoniation conditions forming such products as: 3-(3,5-di-tertbutylpheny1)-2-methylpropene (4), 1-(3,5-di-tert-butylpheny1)-2-methylpropen (5), 3-(33-ditert-butylpheny1)-2-methyl-2-propanol (6), 3-(3,5-di-tert-butylphenyl)-2-butoxy-2-methylpropane (7), 3-(3,5-di-rerr-butylphenyl)-2-methyl-2-trimethyacetoxypropane (8), 2,4,6-tri-terrbutylphenyl trimethylacetate (9), and 2,4,6-tri-tert-butyl-1,4-quinol (10). The major products (47) are accounted for by a free radical pathway by rearrangement of the 2,4,6-tri-rerr-butylphenyl radical. The minor products (esters 8 and 9) probably form by competing ionic reactions. N-Nitroso-2,4,6-tri-tert-butylacetanilide decomposes (at least in part) by a radical pathway leading to the rearranged radical (cH~),&ZH,-A~ which was spin trapped by the nitroso group of the substrate. Spin trapping experiments during the dediazoniation of 2,5-di-rerrbutylaniline similarly gave evidence for the formation of aryl radicals. Une Ctude rpe de la dediazotation de la tri-rert-butyl-2,4,6 aniline avec le nitrite de butyle en solution dans le chlorure de mkthyle indique qu'il y a formation du radical tri-terr-butyl-2,4,6 phenyle dont le spin est piige par le nitrile de butyle. Il y a aussi formation du radical tri-rert-butyl-2,4,6 phenoxyle. Une Ctude des produits formes lors de reactions catalysees par I'acide pivalique indique qu'il se produit, dans les conditions de didiazotation, une nouvelle transposition d'un groupe ortho rert-butyle conduisant a la formation des produits suivants:(di-tert-butyl-3,5 phCny1)-3 methyl-2 propkne (4), (di-tert-butyl-3,5 phCny1)-l methyl-2 propene (5), (di-tert-butyl-3.5 phCny1)-3 methyl-2 propanol-2 (6), (di-tert-butyl-3,5 phenyl)-3 butoxy-2 methyl-2 propane (9, (di-terr-butyl-3,5 phenyl)-3 methyl-2 trimethylacCtoxy-2 propane (8), trimethylacitate de tri-rert-butylphCny1e-2,4,6 (9) et tri-tert-butyl-2,4,6 quinol-1,4 (10). On peut expliquer la formation des produits principaux (47) a I'aide du chemin rtactionnel radicalaire impliquant une transposition du radical tri-rert-butyl-2,4,6 phenyle. Les produits mineurs (esters 8 et 9) se forment probablement par des reactions ioniques en competition. Le N-nitroso tri-terr-butyl-2,4,6 acetanilide se decompose (au. moins en partie) par un mecanisme ridicalaire conduisant au radical transpose (CH3),CCHZ-Ar dont le spin est pikg6 par un groupe nitroso du substrat. Des experiences de piegeage de spin au cours de la didiazotation de la di-tert-butyl-2,5 aniline fournissent des donnees relatives a la formation de radicaux aryles.[Traduit par le journal]

show abstract

Section: Discussionmentioning

confidence: 89%

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

Barclay¹,

Briggs²,

Briggs³

et al. 1979

Can. J. Chem.

View full text Add to dashboard Cite

show abstract

“…The reaction products are all known, well-characterized commonly available compounds. 2,4-(Bis)phenylazophenol 68 and 2-methyl-4-azophenylphenol 25 69 were prepared by the literature methods as cited. In every case, the compounds were obtained and their 1 H, 13 C NMR spectra and mass spectra examined to ensure conformity with literature values.…”

Section: Methodsmentioning

confidence: 99%

Amidine Nitrosation

Loeppky

2004

J. Org. Chem.

View full text Add to dashboard Cite

The acidic nitrosation chemistry of nine acyclic secondary and tertiary amidines (Ph-N=C(R(1))NR(2)R(3); R(1) = H, CH(3), Ph; R(2), R(3) = H, Ph or (CH(3))(2) or C(CH(2))(4)) and several N-acylamidines was investigated. The principal nitrosation products were amides derived from the amino moiety and compounds derived from the benzenediazonium ion, which was independently trapped for quantitation in several cases. Tertiary amidines also produce nitrosamines in minor, but significant, yields. The benzamidines did not react, and the N-acylamidines hydrolyzed much more rapidly than they nitrosated. The data support the hypothesis that the reaction occurs by nitrosation on the imino nitrogen, followed by the addition of H(2)O to give a tetrahedral intermediate (alpha-hydroxynitrosamine) for which the main decomposition pathway generates an amide and a diazonium ion. In the case of the pyrrolidine-derived amidines, about 25% of the decomposition results in cleavage of the amine moiety, which nitrosates to give N-nitrosopyrrolidine. Pseudo-first-order rate constants for amidine nitrosation in aqueous acetic acid with excess nitrite at 25 degrees C ranged from (3 to 106) x 10(-5) s(-1), while the amidine basicity ranged over 5 pK(a) units. Rate constants corrected for amidine basicity showed the pyrrolidine derived amidines to be most reactive. The lack of benzamidine nitrosative reactivity is attributed to a very slow rate of H(2)O additon to the N-nitrosoamidinium ion and reversible nitrosation.

show abstract

“…Polarized benzene and substituted benzenes have been found in CIDNP studies of various dediazoniations (29-33), including pyrolysis of NNA in acetonitrile at low field (34), whereas spin polarized biphenyl from these systems is unusual and was not reported in CIDNP studies even when biaryls were formed in significant yields (33). Both polarized benzene and biphenyl were reported in 13C CIDNP studies of the decomposition of diazoaminobenzene where the enhanced absorption of two carbons of biphenyl was assigned to cage recombination of two phenyl radicals (35). However, spin polarized biphenyl was not found in the 'H CIDNP study of the same system (36).…”

Section: Electron Spin Resonancementioning

confidence: 99%

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

Barclay¹,

Dust²

1982

Can. J. Chem.

View full text Add to dashboard Cite

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]

show abstract

Chemical polarisation of ¹⁵N and ¹³C nuclei in diazo coupling reactions

Cited by 14 publications

References 9 publications

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

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

Amidine Nitrosation

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

Contact Info

Product

Resources

About

Chemical polarisation of 15N and 13C nuclei in diazo coupling reactions

Cited by 14 publications

References 9 publications

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

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

Amidine Nitrosation

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

Contact Info

Product

Resources

About

Chemical polarisation of ¹⁵N and ¹³C nuclei in diazo coupling reactions