Studies on Prototropic Tautomerism in Nitrogen Heterocyclic Compounds. III. : A Stereospecificity in the Ring-Chain Tautomerism including Lactam-NH of a Phthalic Hydrazide Ring

Nakamura, Akitada; Kamiya, Shozo

doi:10.1248/yakushi1947.90.9_1069

Cited by 4 publications

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“…Godin and Le Berre also observed proton signals for two forms, but were not able to identify the isomers 3. Nakamura and Kamiya later published more detailed 1 H NMR results, including the values of coupling constants,6 which were in better agreement with our stereochemical conclusions.…”

Section: Resultssupporting

confidence: 87%

Stereoisomerism and Ring-Chain Tautomerism in 1-Hydroxy-2,3-dihydro-1H-pyrazolo[1,2-a]pyridazine-5,8-diones and 1-Hydroxy- and 1-Amino-2,3-dihydro-1H-pyrazolo[1,2-b]phthalazine-5,10-diones

et al. 2002

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1‐Hydroxy‐2,3‐dihydro‐1H‐pyrazolo[1,2‐a]pyridazine‐5,8diones and 1‐hydroxy‐ and 1‐amino‐2,3‐dihydro‐1H‐pyrazolo[1,2‐b]phthalazine‐5,10‐diones were synthesized and their structures studied by NMR and MS methods. All compounds exist in similar cyclic forms in solution, except for 1hydroxy‐1‐methyl‐2,3‐dihydro‐1H‐pyrazolo[1,2‐a]pyridazine‐5,8‐dione, which displays ring‐chain tautomerism in CDCl3 solution. The corresponding 3‐methyl‐substituted derivatives exhibit a typical cis/trans isomerism as a result of latent ring‐chain‐ring tautomerism. The structures of stereoisomers concluded from NMR results were additionally confirmed by density functional calculations. Mass spectrometric results indicate open‐chain structures in the gas phase for the molecular ions of the 1‐hydroxy derivatives and cyclic structures for 1‐amino derivatives. (© Wiley‐VCH Verlag GmbH, 69451 Weinheim, Germany, 2002)

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Section: Resultssupporting

confidence: 87%

Stereoisomerism and Ring-Chain Tautomerism in 1-Hydroxy-2,3-dihydro-1H-pyrazolo[1,2-a]pyridazine-5,8-diones and 1-Hydroxy- and 1-Amino-2,3-dihydro-1H-pyrazolo[1,2-b]phthalazine-5,10-diones

et al. 2002

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“…The same trend was also observed in the shifts of the methyl protons. These effects were also observed for our starting materials I [4] and they were also seen clearly in the spectra of compounds VaϪc (Table 3), in which the cyclic forms were present in larger amounts (vide infra).…”

Section: -Hydrazino-3-methyl-23-dihydro-1h-pyrazolo[12-a]pyridazine-58-diones Iva؊csupporting

confidence: 70%

1H and 13C NMR Study of 1-Hydrazino-2,3-dihydro-1H-pyrazolo[1,2-a]pyridazine-5,8-diones and -1H-pyrazolo[1,2-b]phthalazine-5,10-diones and Their Ring-Chain Tautomerism

et al. 2002

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Treatment of 1-hydroxy-2,3-dihydro-1H-pyrazolo[1,2-a]pyridazine-5,8-diones and -1H-pyrazolo[1,2-b]phthalazine-5,10-diones with hydrazides produces corresponding acylhydrazino derivatives. In this work, ten new hydrazino derivatives were synthesized, and their properties were studied by 1 H and 13 C NMR spectroscopy. These compounds exhibited several types of structural variation, including ring-chain tautomerism, cis-trans isomerism with respect to the substituents in the pyrazole ring, and (E)/(Z) rotamerism with respect to the nitrogen−carbon hydrazide bond with partial double-

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Phthalazines

Patel¹

1973

Chemistry of Heterocyclic Compounds: A Series of Monographs

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Studies on Prototropic Tautomerism in Nitrogen Heterocyclic Compounds. III. : A Stereospecificity in the Ring-Chain Tautomerism including Lactam-NH of a Phthalic Hydrazide Ring

Cited by 4 publications

References 0 publications

Stereoisomerism and Ring-Chain Tautomerism in 1-Hydroxy-2,3-dihydro-1H-pyrazolo[1,2-a]pyridazine-5,8-diones and 1-Hydroxy- and 1-Amino-2,3-dihydro-1H-pyrazolo[1,2-b]phthalazine-5,10-diones

Stereoisomerism and Ring-Chain Tautomerism in 1-Hydroxy-2,3-dihydro-1H-pyrazolo[1,2-a]pyridazine-5,8-diones and 1-Hydroxy- and 1-Amino-2,3-dihydro-1H-pyrazolo[1,2-b]phthalazine-5,10-diones

1H and 13C NMR Study of 1-Hydrazino-2,3-dihydro-1H-pyrazolo[1,2-a]pyridazine-5,8-diones and -1H-pyrazolo[1,2-b]phthalazine-5,10-diones and Their Ring-Chain Tautomerism

Phthalazines

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