High resolution NMR investigation of enolization of ethyl α-alkylacetoacetates and 3-alkylacetylacetones with branched substituents

Yoffe, S.T.; Fedin, É. I.; Petrovskii, P. V.; Кабачник, М. И.

doi:10.1016/s0040-4039(00)62003-8

Cited by 21 publications

(2 citation statements)

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“…Recently (2) it has been noted that the less stable isomer, also referred to as "cis", can be converted to the more stable "trans" isomer by heating. It was reported also that the n.m.r.…”

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confidence: 99%

Eistert's Methyl Enol Ethers of Acetylacetone

Awang¹

1971

Can. J. Chem.

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The configuration and conformation of the two isomeric methyl en01 ethers of acetylacetone (1) have been unequivocally demonstrated. The n.m.r. solvent shift data and observation of nuclear Overhauser effects support an s-cis conformation for the more stable isomer 2 bearing acetyl trans to methoxyl while indicating an s-trans conformation for the less stable en01 ether 3 having acetyl cis to methoxyl. The facile acid-catalyzed isomerization of 3 to 2 apparently proceeds by reversible protonation of carbony1 oxygen since no deuterium incorporation is observed when the isomerization is performed in acetic acid-d4.La configuration et la conformation des deux ethers methyl Bnoliques de l'acetylacktone (1) ont kt6 demontrees sans ambiguite possible. La r.m.n., les donnees relatives aux deplacements chimiques par les solvants ainsi que I'observation de l'effet nucleaire Overhauser confirment une conformation s-cis pour I'isomere le plus stable (2) ayant le groupe acetyle en position trans par rapport au groupement mtthoxyle. Une conformation s-trans est attribute a 1'6ther Bnolique le moins stable (3) ayant le groupe acttyle en position cis par rapport au groupe methoxyle. L'isomerisation acido-catalyste trts facile de 3 en 2 prodde apparemment par une protonation reversible de I'oxygene du carbonyle puisqu'aucune incorporation de deuttrium n'est observee lorsque I'isom6risation est effectuee dans l'acide ac6tique-d4.

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“…Recently (2) it has been noted that the less stable isomer, also referred to as "cis", can be converted to the more stable "trans" isomer by heating. It was reported also that the n.m.r.…”

mentioning

confidence: 99%

Eistert's Methyl Enol Ethers of Acetylacetone

Awang¹

1971

Can. J. Chem.

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“…The two keto-enole tautomers are generally of similar energies and are transformed one to the other by proton transfer through an intramolecular O-H•••O hydrogen bond. The stability of the tautomers has been shown to be affected by the nature of the R1, R2 and R3 substituents [38][39][40][41][42][43], but also, in solution, by the solvent used, which indicates the effect which the supramolecular surroundings can have on the tautomeric equilibrium of β-diketones [44,45]. For our study, we have decided to cocrystallise two β-diketones (benzoyl-3pyridoylmethane (b3pm) and benzoyl-4-pyridoylmethane (b4pm)) with perfluorinated iodobenzenes (pentafluoroiodobenzene (ipfb), 1,2-tetrafluorodiiodobenzene (12tfib), 1,4-tetrafluorodiiodobenzene (14tfib), 1,3-tetrafluorodiiodobenzene (13tfib) and 1,3,5trifluorotriiodobenzene (135tfib)) [46][47][48] as halogen bond donors (Figure 2).…”

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confidence: 99%

Tautomeric Equilibrium of an Asymmetric β-Diketone in Halogen-Bonded Cocrystals with Perfluorinated Iodobenzenes

et al. 2021

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In order to study the effect of halogen bond on tautomerism in β-diketones in the solid-state, we have prepared a series of cocrystals derived from an asymmetric β-diketone, benzoyl-4-pyridoylmethane (b4pm), as halogen bond acceptor and perfluorinated iodobenzenes: iodopentaflourobenzene (ipfb), 1,2-, 1,3- and 1,4-diiodotetraflorobenzene (12tfib, 13tfib and 14tfib) and 1,3,5-triiodo-2,4,6-trifluorobenzene (135titfb). All five cocrystals are assembled by I···N halogen bonds involving pyridyl nitrogen and iodoperfluorobenzene iodine resulting in 1:1 (four compounds) or 1:2 (one compound) cocrystal stoichiometry. Tautomer of b4pm in which hydrogen atom is adjacent to the pyridyl fragment was found to be more stable in vacuo than tautomer with a benzoyl hydroxyl group. This tautomer is also found to be dominant in the majority of crystal structures, somewhat more abundantly in crystal structures of cocrystals in which additional I···O halogen bond with the benzoyl oxygen has been established. Attempts have also been made to prepare an equivalent series of cocrystals using a closely related asymmetric β-diketone, benzoyl-3-pyridoylmethane (b3pm); however, all attempts were unsuccessful, which is attributed to more effective crystal packing of b3pm isomer compared to b4pm, which reduced the probability of cocrystal formation.

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Keto–enol equilibrium constants

Toullec

1990

PATAI'S Chemistry of Functional Groups

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High resolution NMR investigation of enolization of ethyl α-alkylacetoacetates and 3-alkylacetylacetones with branched substituents

Cited by 21 publications

References 9 publications

Eistert's Methyl Enol Ethers of Acetylacetone

Eistert's Methyl Enol Ethers of Acetylacetone

Tautomeric Equilibrium of an Asymmetric β-Diketone in Halogen-Bonded Cocrystals with Perfluorinated Iodobenzenes

Keto–enol equilibrium constants

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