An ESR and ENDOR study of intramolecular and intermolecular addition reactions of benzoyl and substituted benzoyl radicals to nitroaromatic compounds. A two-step oxygen atom abstraction reaction.

Janzen, Edward G.; Oehler, Uwe M.

doi:10.1016/s0040-4039(00)81494-x

Cited by 22 publications

(11 citation statements)

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“…ENDOR spectra of the DMPO-type radical adducts ENDOR spectra of a variety of 5-membered ring (i.e., pyrrolidine) aminoxyls have appeared in the literature. For instance, pyrrolidine spin labels and spin probes (33,40,45,53,54,64) as well as the heteroatom substituted 3-aza (53), 3-oxa (53,57), 3-aza-N-oxide (imidazole-type) (48), 3-aza and 2-oxa 4,5-aryl fused (36,49) analogues have been successfully analyzed by ENDOR spectroscopy. It is noteworthy that all of the above studies have involved 2,2,5,5-tetra-a-substituted aminoxyls, which are indefinitely stable compounds.…”

Section: Resultsmentioning

confidence: 99%

The first ¹H and ¹⁴N ENDOR spectra of an oxygen-centered radical adduct of DMPO-type nitrones

Haire¹,

Oehler²,

Goldman³

et al. 1988

Can. J. Chem.

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. Can. J. Chem. 66, 2395 (1988). ~, We report the first 'H and ' 4~ electron nuclear double resonance (ENDOR) spectra of oxygen-centered radical adducts (i.e.,derived from the addition of tert-butoxyl radicals) of 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) as well as the related cyclic nitrones: 4-phenyl-5,5-dimethyl-1-pyrroline-N-oxide (4-Ph-DMPO) and 3,3,5,5-tetramethyl-1-pyrroline-N-oxide (M4PO).Features of the electron paramagnetic resonance (EPR) and ENDOR spectra of these cyclic (pyrrolidine) aminoxyl (nitroxide) species along with some deuterated analogues in liquid toluene solutions are highlighted. For instance, we found several long-range y-H hyperfine splittings (HFS's) detectable by ENDOR that provide unique spectral signatures for these radical adducts. Conformational assignments of the pyrrolidine aminoxyl structures based upon the EPR and ENDOR findings are also discussed. Signs of the various hyperfine splittings (i.e., aN, a;, a : ) investigated by cross-relaxation intensity sequence patterns (CRISP) in the ENDOR spectra are also presented. [Traduit par la revue]

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Section: Resultsmentioning

confidence: 99%

The first ¹H and ¹⁴N ENDOR spectra of an oxygen-centered radical adduct of DMPO-type nitrones

Haire¹,

Oehler²,

Goldman³

et al. 1988

Can. J. Chem.

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“…Electron transfer processes are affected by the electron affinity of the acceptor and the ionization energy of the electron donor. In our case, the resulting o ‐methyl, o ‐nitro benzoyl radical is an extremely stable species . This stabilization has been shown to originate from intramolecular trapping of the carbon centered radical by the neighboring nitro group to produce the cyclic acyloxy aminoxyl structure shown in Scheme .…”

Section: Resultsmentioning

confidence: 66%

“…This stabilization has been shown to originate from intramolecular trapping of the carbon centered radical by the neighboring nitro group to produce the cyclic acyloxy aminoxyl structure shown in Scheme . In solution phase, the lifetime of this radical is measured in days . On the other hand, the ability of phenethylamines to serve as electron donors depends on the energy of their highest occupied molecular orbital which is related to the ionization energy.…”

Section: Resultsmentioning

confidence: 99%

Collision‐induced dissociation of phenethylamides: role of ion‐neutral complexes

Nikolić

Macias

Lankin

et al. 2017

Rapid Comm Mass Spectrometry

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RATIONALE Phenethylamides are a large group of naturally occurring molecules found both in the plant and animal kingdoms. In addition, they are used as intermediates for the synthesis of pharmaceutically important dihydro- and tetrahydroisoquinolines. To enable efficient characterization of this class of molecules, a detailed mass spectrometric fragmentation study of a broad series of analogs was carried out. METHODS The test compounds were synthesized using standard methods for amide bond formation. Low energy high resolution tandem mass spectra were acquired on a hybrid quadrupole/time-of-flight mass spectrometer using positive ion electrospray ionization. RESULTS A total of 26 analogs were investigated in the study. Fragmentation of phenethylamides was found to proceed via intermediate ion-neutral complexes. The complexes can break down via multiple pathways including dissociation, proton transfer, Friedel-Crafts acylation, and single electron transfer. The relative contribution of each of these pathways strongly depends on the structure of the coupling amine and acid. CONCLUSIONS A general scheme for the fragmentation of phenethylamides was developed. This study further extends the knowledge base of the ion-neutral complex by discovering Friedel-Crafts acylation as a novel reaction. The strong influence of minor structural modifications on the fragmentation patterns highlights the importance of testing many analogs in order to fully predict a fragmentation pattern of a particular class of molecules.

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“…Based on the prior report of formation of a stable benzoyl nitroxyl radical from 1,3 dinitrobenzene 100, [37] the amidation of 97 with several dinitrobenzenes was also accomplished to obtain amide 106 (Scheme 37). The mechanistic output allowed extending the scope of amidation of aryl α-ketocarboxylic acids with nitroso compounds 101.…”

Section: Amidation Of Acidsmentioning

confidence: 99%

Direct Access to Amides from Nitro‐Compounds via Aminocarbonylation and Amidation Reactions: A Minireview

Barak

Batra

2021

The Chemical Record

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The ubiquity of the amide bond in functional molecules including proteins, natural products, pharmaceuticals, agrochemicals and materials provides impetus to design and develop newer strategies for the generation of this linkage. Owing to growing awareness about sustainability and development of benign strategies, the traditional route of synthesis of amides via reaction between carboxylic acids and amines in the presence of stoichiometric amount of coupling reagents is tagged to be harsh and wasteful. In one of the unconventional routes, nitro compounds are used directly as amine surrogates for preparing amides mostly via aminocarbonylation and amidation reactions. Typically, such processes involves nitroarenes owing to their propensity to transform into nitroso, hydroxylamine, diazo, hydrazine or aniline intermediates in situ under the influence of suitable catalyst or oxidant. This short review provides the comprehensive overview of these reactions including insight into the scope and their mechanisms.

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An ESR and ENDOR study of intramolecular and intermolecular addition reactions of benzoyl and substituted benzoyl radicals to nitroaromatic compounds. A two-step oxygen atom abstraction reaction.

Cited by 22 publications

References 9 publications

The first ¹H and ¹⁴N ENDOR spectra of an oxygen-centered radical adduct of DMPO-type nitrones

The first ¹H and ¹⁴N ENDOR spectra of an oxygen-centered radical adduct of DMPO-type nitrones

Collision‐induced dissociation of phenethylamides: role of ion‐neutral complexes

Direct Access to Amides from Nitro‐Compounds via Aminocarbonylation and Amidation Reactions: A Minireview

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An ESR and ENDOR study of intramolecular and intermolecular addition reactions of benzoyl and substituted benzoyl radicals to nitroaromatic compounds. A two-step oxygen atom abstraction reaction.

Cited by 22 publications

References 9 publications

The first 1H and 14N ENDOR spectra of an oxygen-centered radical adduct of DMPO-type nitrones

The first 1H and 14N ENDOR spectra of an oxygen-centered radical adduct of DMPO-type nitrones

Collision‐induced dissociation of phenethylamides: role of ion‐neutral complexes

Direct Access to Amides from Nitro‐Compounds via Aminocarbonylation and Amidation Reactions: A Minireview

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The first ¹H and ¹⁴N ENDOR spectra of an oxygen-centered radical adduct of DMPO-type nitrones

The first ¹H and ¹⁴N ENDOR spectra of an oxygen-centered radical adduct of DMPO-type nitrones