The radical ions of 4,5,7,8-tetramethyl[2.2]paracyclophane

Bruhin, J.; Gerson, Fabian; Ohya-Nishiguchi, Hiroaki

doi:10.1039/p29800001045

Cited by 11 publications

(9 citation statements)

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“…It necessarily involves intramolecular shift of the two Me groups from the 'inner' to the 'outer' positions of the carbon framework, the 1,6or l&dialkyl substitution being particularly effective in stabilizing Rearrangement of l', 2', and 3' to 6' is more intricate than that of 4' to 6?, because starting from 1, 2, and 3 no paramagnetic species are detected by ESR spectroscopy, except the final product 6'. It is now clear that the spectrum previously attributed to the monomeric radical cation 1' [2] is, in fact, due to 6' and that all three isomeric tetramethyl[2.2]paracyclophanes 1, 2, and 3 do not form persistent radical cations upon oxidation with AlC1, in CH,Cl,. The conversion of these short-lived radical cations into 6' must proceed via several intermediates.…”

Section: Rearrangements Of Radical Cations Of [22]paracyclophanes Anmentioning

confidence: 93%

“…It is now clear that the spectrum previously attributed to the monomeric radical cation 1' [2] is, in fact, due to 6' and that all three isomeric tetramethyl[2.2]paracyclophanes 1, 2, and 3 do not form persistent radical cations upon oxidation with AlC1, in CH,Cl,. The conversion of these short-lived radical cations into 6' must proceed via several intermediates.…”

Section: Rearrangements Of Radicalmentioning

confidence: 93%

“…- in CH,C12/CF,COOH/(CF,CO)20 (10: 1:l) at 193 K leads to the dimeric radical cation 12?. Under more rigorous conditions, such as dissolution of 1 in molten SbC1, or its reaction with AlCl, in CH,Cl, at 353 K, another well-defined ESR spectrum was observed [2]; this has been attributed to the monomeric radical cation 1'. Later on, however, doubt was cast on this interpretation, because an analogous treatment of the isomeric 4,7,13,16-tetrarnethyl[2.2]paracyclophane (5,11,13, [4] which was identical with that previously attributed to It.…”

Section: Rearrangements Of Radical Cations Of [22]paracyclophanes Anmentioning

confidence: 99%

“…-Source qfcompounds. The syntheses of 1 [2], 2 [12][15], 3 [16], and 4 [9] have been described elsewhere. Compound 6 was prepared via 5,7,14,16-tetramethy1-2,1 l-dith~d[3.3]metacyclophane (6,8,14,16-tetramethyl-3.1l-dithiatricyclo[ 1 I ,3,1,15~y]octadeca-l( 17), 5,7,9( 18),13,15-hexaene) and 4,6,12,14tetramethyl[2.2]metacyclophane-1,9-diene (5,7,12,14-tetramethyltricycl0[9.3.1.…”

Section: -4"mentioning

confidence: 99%

“…14.8]hexadeca-l (1 5),2,4,6,8( 16), 9,11,13-octaene), according to a procedure introduced by Mitchell and Boekelheide [9]. Synthesis of 10 was accomplished by coupling 1,3-bis(bromomethyl)benzene [ 171 with the K salt of 2,3,5,6-tetrarnethyl-1,4bis(mercaptomethy1)benzene [2] and expulsion of the two S-atoms from the thus formed 14,15,17,18-tetramethylL2,l l-dithia Instrumental. The ESR spectra were taken on Vurian-E9 instrument, while Bruker ESP-300 spectrometer served for the ENDOR and TRIPLE-resonance studies.…”

Section: -4"mentioning

confidence: 99%

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Rearrangements of Radical Cations of [2.2]Paracyclophanes and of a bridged [14]annulene to those of pyrenes: An ESR and ENDOR study

Gerson

Huber

Wellauer

1989

Helvetica Chimica Acta

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ESR and ENDOR studies have been carried out on the radical cations obtained consecutively by reaction of rrans-lob, 10c-dimethyl-lob, 10c-dihydropyrene (4) with AICI, in CH,CI,. The primarily formed 4' rearranges at 253 K to the radical cation(s) of 1.6-(5a) and/or 1,8-dimethylpyrene (5b). At 323 K, the spectra of 5a'/5b' are replaced by that of the highly persistent radical cation of 1,3,6&tetramethylpyrene (6). Surprisingly, 6' is also the only observable paramagnetic product resulting from a treatment of 4,5,7,8-(l), 4,7,13,16-

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Section: Rearrangements Of Radical Cations Of [22]paracyclophanes Anmentioning

confidence: 93%

Section: Rearrangements Of Radicalmentioning

confidence: 93%

Section: Rearrangements Of Radical Cations Of [22]paracyclophanes Anmentioning

confidence: 99%

Section: -4"mentioning

confidence: 99%

Section: -4"mentioning

confidence: 99%

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Rearrangements of Radical Cations of [2.2]Paracyclophanes and of a bridged [14]annulene to those of pyrenes: An ESR and ENDOR study

Gerson

Huber

Wellauer

1989

Helvetica Chimica Acta

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ChemInform Abstract: THE RADICAL IONS OF 4,5,7,8‐TETRAMETHYL(2.2)PARACYCLOPHANE

Bruhin¹,

Gerson²,

Ohya-Nishiguchi³

1980

Chemischer Informationsdienst

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The Radical Anions of [2.2]Paracyclophane‐1,9‐diene and Some of its Derivatives. An Unexpected Conformational Interconversion

Bruhin

Gerson

Möckel

et al. 1985

Helvetica Chimica Acta

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Dedicated to Prof. Virgil Boekelheide on the occasion of his 65th birthday (27.XII.84) ~The radical anions of [2.2]paracyclophane-1,9-diene (2) and its 1,10,12,13,15,16-hexadeuterio derivative 2-D6, as well as those of 4,5,7,8-tetramethyl[2.2]paracyclophane-l,9-diene (3) and its 12,13,15,16-tetradeuterio derivative 3-D4, have been studied by ESR spectroscopy. The coupling constants for 2: at 178 K are 0.422 mT for four equivalent olefinic protons and 0.046 and 0.020 mT, each for a set of four equivalent aromatic protons. This hyperfine pattern is consistent with either benzene ring bearing two pairs of equivalent protons and it points to a lowering of the anticipated D,, symmetry. The ESR spectra of 2: are strongly temperature dependent, due to modulation of the two coupling constants of 0.046 and 0.020 mT; these have opposite signs and average to 0.013 mT at 273 K. The experimental findings are interpreted in terms of a transition state of D2h symmetry, 33 kJ/mol above two interconverting equivalent conformations of lower symmetry. Several pieces of evidence suggest that this symmetry is D,, i.e., the benzene rings in 2: are twisted in opposite directions about the vertical axis. Temperature dependence of the ESR spectra, resulting from modulation of the hyperfine interactions with the aromatic protons, is also observed for 2-D6; and 37. In the case of 3', the olefinic protons are, as expected, only equivalent in pairs, the pertinent coupling constants being 0.560 and 0.325 mT. Upon standing at low temperatures, 2; and 3: gradually convert into the radical anions of [2.2]paracyclophane (1) and its 4,5,7,8-tetramethyl derivative, respectively. At higher temperatures, cleavage of one bridging chain in 2: also occurs, with the formation of the radical anion of (E)-4,4'-dimethylstilbene (7). Both reactions of 27 must involve the transient radical anion of [2.2]paracyclophane-l-ene (4) as proved by the observation of the spectra of 1 : and 7: with 4 as the starting material.Introduction. -Replacement of the single by the double bonds in the two bridging alkyl chains of [2.2]paracyclophane (l), to yield the 1,9-diene 2, has only a small effect on the geometry and electronic structure. As shown by the X-ray analyses of 1 [I] and 2 [2],

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The radical ions of 4,5,7,8-tetramethyl[2.2]paracyclophane

Cited by 11 publications

References 0 publications

Rearrangements of Radical Cations of [2.2]Paracyclophanes and of a bridged [14]annulene to those of pyrenes: An ESR and ENDOR study

Rearrangements of Radical Cations of [2.2]Paracyclophanes and of a bridged [14]annulene to those of pyrenes: An ESR and ENDOR study

ChemInform Abstract: THE RADICAL IONS OF 4,5,7,8‐TETRAMETHYL(2.2)PARACYCLOPHANE

The Radical Anions of [2.2]Paracyclophane‐1,9‐diene and Some of its Derivatives. An Unexpected Conformational Interconversion

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