Synthesis and study of pseudoaromatic compounds. X. A reevaluation of the question of aromatic character in tropone, tropolone, and substituted heptafulvenes based on the analysis of the nuclear magnetic resonance spectra of these and several related compounds

Bertelli, Domenick J.; Andrews, Tim; Crews, Phillip

doi:10.1021/ja01047a018

Cited by 129 publications

(27 citation statements)

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“…The plnr spectrum of the rearranged product, 4H, was identical in all respects to that obtained by protonation of authentic 4 (5). Cyclohepta-2,4-dienone, 4, was obtained on careful neutralization of the acid solution and this was identical in all respects to an authentic sample (5,9). Other acids, such as FS03H or H2SO4, could be used to effect this isomerization; however, with H2S04 some charring occurred on the initial dissolution.…”

Section: Resultsmentioning

confidence: 91%

The formation of cycloheptenone and cycloheptadienones from bicyclo[3.2.0]heptanone derivatives. An acid-catalyzed, two carbon ring expansion reaction

Hine¹,

Childs²

1976

Can. J. Chem.

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In strong acids, such as FSO3H and 96% HzS04, bicyclo[3.2.0]heptan-6-one and bicyclo-[3.2.0]hept-2-en-7-one undergo a clean isomerization to form protonated cyclohept-2-enone and cyclohepta-2,4dienone, respectively. Substituted derivatives undergo comparable ring expansions when dissolved in these strong acids. The seven-membered ring ketones can be recovered on quenching the acid solutions with a NaHCO3-ether mixture. In contrast, bicyclo-[3.2.0]hept-2-en-6-one when dissolved in FSO3H rearranged to give protonated l-acetylcyclopentadiene. The mechanism and synthetic utility of these reactions is discussed. KENNETH E. HINE et RONALD F. CHILDS. Can. J. Chem. 54, 12 (1976).Dans les acicies forts comme FSO3H et HlS04 96y0 la bicyclo[3.2.0]heptanone-6 et la bicyclo[3.2.0]heptkne-2 one-7 subissent des isornerisatio~~s propres conduisant respectivement aux formes protonCes de la cycloheptkne-2 one et de la cycloheptadikne-2,4 one. Des derives portant des substituants subissent des extensions de cycle comparables lorsque dissous dans ces acides forts. On peut rCcupCrer les cCtones cycliques a sept chainons en traitant les solutions acides par un melange NaHCOs-Cther. Par ailleurs le traitement de la bicycIo[3.2.O]heptkne-2 one-6 par FSO3H conduit k la forme protonee de l'acetyl-1 cyclopentadikne. On discute du mecanisme et de l'utilite en synthiese de ces reactions.[Traduit par le journal]There are numerous examples of fused bicyclic ring systems in which one of the rings is a cyclobutanone moiety. Indeed, one common and facile synthetic entry into this type of ring system involves the cycloaddition of a ketene to a cycloalkene (I). If a means could be found of inducing cleavage of the cyclobutanone bond that is conunon to both rings, then combined with this ketene addition, we would have a route t o functionalized monocyclic systems possessing a ring two carbons larger than that of the alkene used in the original cycloaddition. A viable two carbon ring expansion reaction would be of value in general syntheses of medium size rings (2). The well known interconversion of cyclobutyl, cyclopropylcarbinyl, and open chain cationic systems (3) suggested t o us that one method of inducing the desired cleavage of the cyclobutanone bond would be to react this carbonyl function with an electrophile. There are several reports of the isomerization of cyclobutanones upon protonation and it would appear that in nlany of these rearrangements the carbon-carbon bond / 3 to the carbonyl group is cleaved (4). In view of our interest in the chemistry of the monocyclic, unsaturated, seven-membered ring ketones (5), we have examined the effect of protonation on several bicyclo[3.2.0]heptan-6-ones and bicyclo[3.2.0Jheptenones and report here the results of this study. ResultsCareful solution of bicyclo[3.2.0]heptan-6-one, 1, in FS03H at -78 "C yielded a clear yellow solution whose pmr spectrum at +20 "C (

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Section: Resultsmentioning

confidence: 91%

The formation of cycloheptenone and cycloheptadienones from bicyclo[3.2.0]heptanone derivatives. An acid-catalyzed, two carbon ring expansion reaction

Hine¹,

Childs²

1976

Can. J. Chem.

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“…The spectrum is not only phase twisted,but it also has the wrong structure showing cross peaks even though no motion was assumed in the calculation. No combinationof the echo and anti-echosignalscan there- (30) '…”

Section: B Elimination Ofphase Twistmentioning

confidence: 99%

Rotor Synchronized MAS Two‐Dimensional Exchange NMR in Solids. Principles and Applications

Luz

Spieß

Titman

1992

Israel Journal of Chemistry

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Abstract. The principles of the rotor synchronized magic angle spinning (MAS) two-dimensional exchange NMR, first proposed by Veeman and coworkers are reviewed, with particular emphasis on situations where chemical exchange in solids proceeds in concert with molecular reorientation. Calculations of 9'0ss peak intensities as function of the ratio between the chemical shift anisotropy and the spinning rate are presented for several cases. These calculations emphasize the advantage of using slow spinning rates (OlR < OlL~cr) in such experiments when detailed information about mechanistic pathways in solids is sought. Three applications of the method to solid systems using carbon-13 NMR are described. These include: (a) Trimethylsulfoxonium iodide, in which the molecules undergo 120 0-jumps about the molecular C 3 symmetry axis; (b) Tropolone, where the tautomeric hydrogen shift is found to be a consequence of the self diffusion within the crystal lattice. and in general accompanied by molecular reorientation. Here the two-dimensional pattern is used to obtain information about the various mechanisms of the diffusion process; (c) Bullvalene, where a quantitative analysis of the cross peak intensities as function of the mixing time provides kinetic information on two independent processes, viz. symmetric threefold jumps and a concerted Cope rearrangement-molecular reorientation reaction.

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“…In each case the spectra were in agreement with a symmetrical spin system, and better spectral fits were not possible by removing the symmetry constraint. The scalar coupling constants J0" were taken from the analysis of the molecule in a normal solvent [3], and the spectra fitted using the hamiltonian,…”

Section: Analysis Of Spectramentioning

confidence: 99%

The N.M.R. spectrum of tropolone dissolved in nematic solvents. An exchanging spin system

1974

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Synthesis and study of pseudoaromatic compounds. X. A reevaluation of the question of aromatic character in tropone, tropolone, and substituted heptafulvenes based on the analysis of the nuclear magnetic resonance spectra of these and several related compounds

Cited by 129 publications

References 1 publication

The formation of cycloheptenone and cycloheptadienones from bicyclo[3.2.0]heptanone derivatives. An acid-catalyzed, two carbon ring expansion reaction

The formation of cycloheptenone and cycloheptadienones from bicyclo[3.2.0]heptanone derivatives. An acid-catalyzed, two carbon ring expansion reaction

Rotor Synchronized MAS Two‐Dimensional Exchange NMR in Solids. Principles and Applications

The N.M.R. spectrum of tropolone dissolved in nematic solvents. An exchanging spin system

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