The Radical Cation of Azatriquinane: An ESR Study

Gerson, Fabian; Merstetter, Pascal; Mascal, Mark; Hext, Nicholas M.

doi:10.1002/(sici)1522-2675(19981007)81:10<1749::aid-hlca1749>3.0.co;2-3

Cited by 8 publications

(17 citation statements)

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“…Treatment of 34 in THF-d 8 with excess n-BuLi at -78 °C resulted in the disappearance of the protons  to nitrogen and a downfield chemical shift of the vinyl protons from  = 5.77 ppm to 6.28 ppm. This observation is consistent with a diatropic ring current which, along with corresponding shifts in the 13 C NMR spectrum, confirmed the assignment of the Li + 33 structure. 30 The  values in 33 were also consistent with the ab initio calculated chemical shifts using the gauge independent atomic orbital (GIAO) method to model the shift tensors.…”

Section: Account Synlettsupporting

confidence: 86%

“…The rigidity and symmetrical nature of 39 also made it amenable to analysis by 14 N NMR spectroscopy by suppressing the influence of the quadrupole moment of 14 N on the spin-lattice relaxation time, resulting in a sharp singlet. The 1 H, 13 C, and 14 N NMR spectra were fully consistent with the GIAO-modeled chemical shifts.…”

Section: Account Synlettsupporting

confidence: 61%

“…The data pointed to an oxidative dimer of 7, which X-ray crystallography showed to be the C 2h -symmetric product 16 (Scheme 2), the result of a [3+3] azomethine ylide dimerization. A distinguishing feature of this remarkable diamine is the long C-C distances in the dimer bridges (C6-C9 = 1.585Å) which was manifested in the extreme downfield chemical shift observed in the 13 C NMR spectrum ( = 79.6 ppm in CDCl 3 ) for the participating carbons. Another notable feature is the extreme bond angles (N1-C6-C9A = 100.0° and C5-C6-C9 = 125.3°), which are a consequence of repulsion between the nitrogen lone pair and the adjacent ethylene bridge (Figure 4).…”

Section: Azatriquinanementioning

confidence: 99%

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Chemistry of the Heterotriquinanes and Heterotriquinacenes

Hafezi¹,

Mascal²

2021

Synlett

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Triquinanes are tricyclic hydrocarbons that have fused cyclopentane rings. Although there are linear and angular triquinanes that are doubly fused, this Account focuses exclusively on the ‘triquinacane’, or triply fused structure with a heteroatom (nitrogen or oxygen) on the C 3v symmetry axis. Azatriquinane- and oxatriquinane-based species tend to show remarkable and often unexpected chemistry, and have variously comprised the most basic trialkyl amine, a superbasic proton chelate, trigonal pyramidal ligand platforms, novel calixiform hosts, aromatic hemispheres of hetero-C20 fullerenes, cocrystallizing agents for eliminating rotational disorder in fullerene crystals, the first water-stable, chromatographable trialkyloxonium species, the first isolable allylic oxonium species, world-record C–O bond lengths, rapid SN2 reaction at a tertiary center, and R4O2+ (oxadionium) species.1 Introduction2 Azatriquinane3 Azatriquinacene4 Aromatic Azatriquinacene-Based Systems5 Oxatriquinane6 Tetravalent Oxygen7 Oxatriquinacene8 The Future

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Section: Account Synlettsupporting

confidence: 86%

Section: Account Synlettsupporting

confidence: 61%

Section: Azatriquinanementioning

confidence: 99%

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Chemistry of the Heterotriquinanes and Heterotriquinacenes

Hafezi¹,

Mascal²

2021

Synlett

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“…Radicals 2-33 correspond to N-centered radicals: alkylaminyl radicals (2-8); radical cations of acyclic alkylamines (9)(10)(11)(12)(13)(14)(15)(16)(17)(18); radical cations of cyclic alkylamines (19)(20)(21)(22)(23)(24)(25)(26); iminyl radicals (27)(28)(29)(30)(31); azaphenyl radicals (32 and 33). Radicals 34-63 correspond to NN-centered radicals: alkylhydrazyl radicals (34)(35)(36)(37)(38)(39); radical cations of alkylhydrazines (40)(41)(42)(43)(44)(45)(46)(47)(48)(49)(50)(51)(52)(53); radical cations of alkyldiamines (54)(55)(56)(57); radical ions of alkylazoalkanes (58-63). Radicals 64-106 correspond to NOand NO 2 -centered radicals: alkylnitroxyl radicals (64-79); radical anions of nitroalkanes (80)…”

Section: Computational Detailsmentioning

confidence: 99%

Density Functional Theory Study of ¹⁴N Isotropic Hyperfine Coupling Constants of Organic Radicals

et al. 2006

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Nitrogen hyperfine coupling constants (hfccs) of organic radicals have been calculated by density functional theory (DFT) methodology. The capability of the B3LYP functional, combined with 6-31G*, TZVP and EPR-III basis sets, to reproduce experimental nitrogen coupling constant data has been analyzed for 109 neutral, cationic and anionic radicals, all of them containing at least one nitrogen atom. The results indicate that the selection of the basis set plays an important role in the accuracy of DFT calculations of hfccs, mainly in relation with the composition of the primitive functions and the quantum number of those functions. The main conclusion obtained is the high reliability of the scheme B3LYP/6-31G* for the prediction of nitrogen hfccs with very low computational cost.

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“…might have occurred by the radical CF 3 CCl 2 . formed by loss of a Cl-atom, as the known 28-line hyperfine pattern of this radical (see, e. g., [9]) appeared intermediately at ca. 140 K.…”

Section: Scheme 2 Schemementioning

confidence: 99%

Influence of Ring Annelation on the Mode Selectivity of the Ionized Diazabicycloheptenes and Corresponding Housanes: An ESR and ENDOR Study

Gerson

Şahin

2001

HCA

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Dedicated to Professor Edgar Heilbronner on the occasion of his 80th birthdayThe tricyclic azoalkanes, (1a,4a,4aa,7aa)-4,4a,5,6,7,7a-hexahydro-1,4,8,8-tetramethyl-1,4-methano-1H-cyclopenta[d]pyridazine (1c), (1a,4a,4aa,6aa)-4,4a,5,6,6a-pentahydro-1,4,7,7-tetramethyl-1,4-methano-1H-cyclobuta[d]pyridazine (1d), (1a,4a,4aa,6aa)-4,4a,6a-trihydro-1,4,7,7-tetramethyl-1,4-methano-1H-cyclobuta[d]-pyridazine (1e), and (1a,4a,4aa,5aa)-4,4a,5,5a-tetrahydro-1,4,6,6-tetramethyl-1,4-methano-1H-cyclopropa[d]-pyridazine (1f), as well as the corresponding housanes, the 2,3,3,4-tetramethyl-substituted tricyclo[3.3.0.0 2,4 ]octane (2c), tricyclo[3.2.0.0 2,4 ]heptane (2d), and tricyclo[3.2.0.0 2,4 ]hept-6-ene (2e), were subjected to g-irradiation in Freon matrices. The reaction products were identified with the use of ESR and, in part, ENDOR spectroscopy. As expected, the strain on the C-framework increases on going from the cyclopentane-annelated azoalkanes and housanes (1c and 2c) to those annelated by cyclobutane (1d and 2d), by cyclobutene (1e and 2e), and by cyclopropane (1f). Accordingly, the products obtained from 1c and 2c in all three Freons used, CFCl 3 , CF 3 CCl 3 , and CF 2 ClCFCl 2 , were the radical cations 3c . and 2c . of 2,3,4,4-tetramethylbicyclo[3.3.0]oct-2-ene and 2,3,3,4-tetramethylbicyclo[3.3.0]octane-2,4-diyl, respectively. In CFCl 3 and CF 3 CCl 3 matrices, 1d and 2d yielded analogous products, namely the radical cations 3d . and 2d . of 2,3,4,4-tetramethylbicyclo[3.2.0]hept-2-ene and 2,3,3,4-tetramethylbicyclo[3.2.0]heptane-2,4-diyl. The radical cations 3c . and 3d . and 2c . and 2d . correspond to their non-annelated counterparts 3a . and 3b . , and 2a . and 2b . generated previously under the same conditions from 2,3-diazabicyclo[2.2.1]hept-2-ene (1a) and bicyclo[2.1.0]pentane (2a), as well as from their 1,4-dimethyl derivatives (1b and 2b). However, in a CF 2 ClCFCl 2 matrix, both 1d and 2d gave the radical cation 4d . of 2,3,3,4-tetramethylcyclohepta-1,4-diene. Starting from 1e and 2e, the radical cations 4e . and 4e' . of the isomeric 1,2,7,7-and 1,6,7,7-tetramethylcyclohepta-1,3,5-trienes appeared as the corresponding products, while 1f was converted into the radical cation 4f . of 1,5,6,6-tetramethylcyclohexa-1,4-diene which readily lost a proton to yield the corresponding cyclohexadienyl radical 4f . . Reaction mechanisms leading to the pertinent radical cations are discussed.Introduction. ± In a previous work, ionization of 2,3-diazabicyclo[2.2.1]hept-2-ene (1a) and the corresponding bicyclo[2.1.0]pentane (housane; 2a), as well as of their 1,4-dimethyl derivatives 1b and 2b, respectively, was carried out by g-irradiation in Freon matrices, and the resulting radical cations were studied by ESR spectroscopy [1]. Whereas the azoalkanes 1a and 1b yielded the radical cations of cyclopentene (3a) and its 1,3-dimethyl derivative 3b, respectively, cyclopentane-1,3-diyl radical cations were obtained by starting from the corresponding housanes 2a and 2b (Scheme 1).Despite a considerable weakening of the cent...

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The Radical Cation of Azatriquinane: An ESR Study

Cited by 8 publications

References 9 publications

Chemistry of the Heterotriquinanes and Heterotriquinacenes

Chemistry of the Heterotriquinanes and Heterotriquinacenes

Density Functional Theory Study of ¹⁴N Isotropic Hyperfine Coupling Constants of Organic Radicals

Influence of Ring Annelation on the Mode Selectivity of the Ionized Diazabicycloheptenes and Corresponding Housanes: An ESR and ENDOR Study

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The Radical Cation of Azatriquinane: An ESR Study

Cited by 8 publications

References 9 publications

Chemistry of the Heterotriquinanes and Heterotriquinacenes

Chemistry of the Heterotriquinanes and Heterotriquinacenes

Density Functional Theory Study of 14N Isotropic Hyperfine Coupling Constants of Organic Radicals

Influence of Ring Annelation on the Mode Selectivity of the Ionized Diazabicycloheptenes and Corresponding Housanes: An ESR and ENDOR Study

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Density Functional Theory Study of ¹⁴N Isotropic Hyperfine Coupling Constants of Organic Radicals