Crystal structural determination of ring-chain tautomers of 1,2,3,4-tetrahydro-s-tetrazines

1,2,3,4-Tetrahydro-1-methyl-3-(p-bromophenyl)-4,6-diphenyl-s-tetrazine ( 3a ), exhibiting “ring ? chain” tautomerism in solutions, exists as the ring tautomer in the solid phase, as proved by X-ray crystal structure determination. However, the 6-acetyl analogue 3b acquires the chain form in the crystalline state.     

Mass spectrometric study of ring-chain tautomers of 3-amino(hydroxy)pyrazolidines

The mass spectrometric fragmentation of substituted 3-amino-, 3-hydrazino-, and 3-hydroxypyrazolidines has been studied. In the gas phase these compounds exist partly as the acyclic tautomers.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1334–1338, 1986.     

Mass spectrometric identification of ring-chain tautomers of 4-cyano-3-pyrazolidones in the gas phase

Analysis of the electron impact mass spectra of a series of 4-cyano-3-pyrazolidones, which manifest ring-chain tautomerism in polar solvents, showed that these compounds also exist in the gas phase as a mixture of tautomers, which undergo characteristic fragmentation. The quantitative tautomer ratio in this series is a function of electronic and steric substituent effects. The fragmentation pathways for each of the tautomers were determined using high-resolution mass spectrometry.M. V. Lomonosov Moscow State University, 119899 Moscow. Yerevan State University, 375025 Yerevan. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp 1525–1530, November, 1995 Original article submitted November 1, 1995.     

Reaction of phthalaldehydic acid with different substituted aniline as well as hydrazine derivatives

Phthalaldehydic acid 1 is often represented as having two tautomeric forms 1a and 1b. The reaction of phthalaldehydic acid with different aryl amine and heterocyclic aryl hydrazine derivatives afforded different products depending on the reaction conditions such as solvent and temperature.     

The relative stability of the tautomers of α-Hydroxytetronic acid

The relative stability of the four tautomeric forms of α-hydroxytetronic acid was calculated with full geometry optimization at the STO -3G , 3–21G , 6–31G *, and 6–31G ** SCF levels. Correlation effects were estimated using the MP 2 method. Intramolecular hydrogen bonds are found to be of primary importance for the relative stability of the various tautomers, and the same tautomer that in the case of L -ascorbic acid is experimentally observed in the crystal as well as in solution is found to be the most stable one, if polarization functions on the hydrogen atoms are taken into account. It is concluded that even in the gas phase this tautomer predominates in α-hydroxytetronic acid as well as in L -ascorbic acid. © 1994 John Wiley & Sons, Inc.     

The role of tautomers in the UV absorption of urocanic acid

Tautomeric effects in the UV-absorption of trans-urocanic acid in the gas phase are investigated by means of quantum chemical calculations of sixteen tautomers at different levels, followed by absorption cross section simulations. It is shown that several trans tautomers give significant contributions to the total spectrum and that cis tautomers should not contribute to the spectrum at room temperature. The spectra of tautomers protonated at the N1 site of the imidazole ring are strongly red shifted in comparison to the spectra of tautomers protonated at the N3 site. As a consequence, excitation of the first absorption band at different wavelengths produces very different tautomeric populations. This effect helps to explain specific features observed in dispersion emission spectroscopy as well as the anomalous photophysics of urocanic acid.     

Ring closure reactions involving 1-hydrazinophthalazine. Reactions with 1,2,4-tricarbonyl and 1,3-dicarbonyl compounds

Annelation reactions of six-membered rings to 1-hydrazinophthalazine, 1, were investigated. With aroyl-(acyl)pyruvates, 2, the desired system was obtained. It was found that the course of the reaction depends on the reaction condition as well as the substituted pyruvates. Thus, 3-(2-oxo-2-substituted ethyl)-4H-as-triazino-[3,4-a]phthalazin-4-one, 4, was the product when 1 reacted with 2 in alcoholic medium. The side chain tauto-merism of 4 was studied by using ir, ¹H-nmr, and ms spectral methods. When 1 hydrochloride instead of 1 was reacted with 2, 3-ethoxycarbonyl-s-triazolo[3,4-a]phthalazine, 6, was the major product. The reaction of 1 with benzoylacetone in ethanol afforded the hydrazalone, 9. By ir, ¹H-nmr, and ¹³C-nmr methods it was shown that in solution it is inolved in an enhydrazine-hydrazone as well as a ring-chain tautomerism. Compound 9 upon the action of PPA underwent dehydrative cyclization to 3-methyl-s-triazolo[3,4-a]phthalazine, 10, and 3-methyl-5-phenyl-1-(l-phthalazinyl)pyrazole, 7. The reaction of 1 with ethyl phenylpropiolate in ethanol was reported by others to give 1-(1-phthalazinyl)-3-phenyl-5-pyrazolone, 8. Upon reinvestigation of this reaction it is shown that the product actually is ethyl β-(1-phthalazinylhydrazono)benzenepropanoate, 11. Attempts to synthesize 8 were unsuccessful by this method. In the reaction of 1 with ethyl benzoylacetate the expected hydralazone 11 was easily formed which upon reaction with PPA yielded the desired species 8.     

Protonation of 1,4,5-tri- and 1,4,5,8-tetrahydroxyanthraquinones in sulfuric acid: Multistep reaction involving tautomers and conformers

The fine structure of the ??_l,??*-absorption of hydroxyanthraquinones solutions in sulfuric acid arises due to the existence of the protonated forms as equilibrium mixtures of tautomers and conformers distinguished by the positions of the ??-bonds, charges, and the number of intramolecular hydrogen bonds. Using quantum-chemical calculations and correlation analysis of the absorption spectra tautomers were identified of mono- and dications of 1,4,5-trihydroxyanthraquinone of 9,10-, 1,4-, and 1,10-isomeric structure. For 1,4,5,8-tetrahydroxyanthraquinone 9,10-, 1,4-, 1,10-, and 1,5-isomeric mono- and dications and their conformers were found.     

1-Amino-2-hydrazinopyrimidin-N-ylides. Unusual tautomers of 1-aminopyrimidin-2-hydrazones

Summary 1-Amino-2-methylthiopyrimidinium iodides3 have been synthesized by reaction of 3-isothiocyanato-2-propeniminium perchlorates1 with hydrazines and subsequent methylation of the resulting 1-amino-2(1H)-pyrimidinthiones2. Reaction of3 with hydrazine causes substitution of the methylthio group and results in the formation of deeply coloured 1-amino-2-hydrazinopyrimidin-N-ylides5 as unusual tautomers of the commonly expected 1-amino-2(1H)-pyrimidinhydrazones4. The structure of these N-ylides has been proved by spectroscopic methods as well as by subsequent transformation to 3-amino-1,2,4-triazolo[2,3-a]pyrimidinium salts9 by dehydration or to pyrimidotriazinium salt10 c by oxidation. Reaction of N,N-disubstituted 1-amino-2-methylthiopyrimidinium salt7 a with hydrazine also causes substitution of methylthiol, the resulting orange N,N-disubstituted 1-amino-2(1H)-pyrimidinhydrazone8 a, however, cannot tautomerize to N-ylides.

---

1-Amino-2-hydrazinopyrimidin-N-ylide. Ungewöhnliche Tautomere von 1-Aminopyrimidin-2-hydrazonen

Zusammenfassung Es wurden 1-Amino-2-methylthiopyrimidiniumjodide3 ausgehend von 3-Isothiocyanato-2-propeniminiumperchloraten1 und Hydrazinen durch Methylierung der primär gebildeten 1-Amino-2(1H)-pyrimidinthione2 hergestellt. Die Reaktion dieser Pyrimidiniumsalze3 mit Hydrazin verläuft unter Substitution der Methylthiogruppe unter Bildung violett gefärbter 1-Amino-2-hydrazinopyrimidin-N-ylide5 als ungewöhnliche Tautomere der allgemein erwarteten 1-Amino-2(1H)-pyrimidinhydrazone4. Die Struktur dieser Ylide5 wird durch spektroskopische Methoden sowie durch nachfolgende Dehydratisierung zu 3-Amino-1,2,4-triazolo[2,3-a]pyrimidiniumsalzen9 bzw. Oxydation zum Pyrimidotriaziniumsalz10 c bewiesen. Die Reaktion des N,N-disubstituierten 1-Amino-2-methylthiopyrimidiniumsalzes7 a mit Hydrazin verläuft ebenfalls unter Substitution der Methylthiogruppe. Jedoch kann das gebildete orange gefärbte, N,N-disubstituierte 1-Amino-2(1H)-pyrimidinhydrazon8 a nicht zu einem N-Ylid tautomerisieren.

     

The ring-chain equilibrium in derivatives of 5-nitro-1, 2, 3, 4-tetrahydropyrimidine in trifluoroacetic acid

¹H NMR spectra of derivatives of 5-nitro-1,2,3,4-tetrahydropyrimidine were examined in trifluoroacetic acid solution. It was found that the compounds, unsubstituted in position 2, preserve their ring structure, whereas 2-alkyl- and 2-aryl derivatives are subjected to ring opening.     

The structure of the protonated forms of 1-hydrazinophthalazine and phthalazone hydrazone derivatives

Phthalazone derivatives Ia–h are protonated at the exocyclic nitrogen and phthalazine derivatives IIa–c at the N-2 of the ring. The cations of hydrazones Va–e have the cyclic structures VIa–e.     

Preparation and analytical properties of a chelating resin functionalized with 1-hydrazinophthalazine ligand

A poly[styrene-co-(divinylbenzene)] resin (XAD-4) functionalized with 1-hydrazinophthalazine ligand has been prepared and its analytical properties investigated. The pH dependence of sorption of metal ion on the resin has been determined for Cu(II), Ni(II), Co(II), Zn(II), Cd(II), Pb(II), Fe(III) and Cr(III). Trace amounts of these metal ions were quantitatively retained on the resin and recovered by eluting with 1 mol l(-1) hydrochloric acid. The resin was found to be selective for Fe(III) and its separation from other metal ions was carried out effectively. Metal ions concentrations were determined using AAS.     

Esterification in solution. The reaction of methacrylic acid with glycols

Azeotropic methacrylation of ethylene glycols in solution in the presence of p-toluenesulfonic acid can be described by two irreversible consecutive-competitive second order reactions with a rate constant ratio of to 2. The main reaction may be complicated by esterification of p-toluenesulfonic acid. Under certain conditions this side reaction may become predominant. A possible reason of this phenomenon is suggested.

---

- - 2. -. . .

     

Preparation of 3-hydroxyisoindolin-1-ones and o-acylbenzamides. A study of ring-chain tautomerism

3-Hydroxyisoindolinones (ring form) as well as their chain tautomers, o-acylbenzamides, were prepared from the reactions of 3-benzalphthalide 1 , 3-halophthalides 3 , and o-acylbenzoic acids 6 or their esters 7 with amines 2 , and those of phthalimides 4 with Grignard reagents 5 . The characteristic spectroscopic properties of ring and chain forms are observed in the ir and ¹³C-nmr spectra. The significance of the spectroscopic results is discussed, as is the relationship between the structure of the products and the position of the ring-chain equilibrium.     

New type of ring-chain tautomerism. Direct evidence from 1H NMR spectroscopy

A new type of ring-chain tautomerism consisting in the reversible transformation of 4-(5-)haloalkanecarboxylic acid dialkylamides into dialkyl(tetrahydrofuran-2-ylidene)- and dialkyl(tetrahydropyran-2-ylidene)ammonium halides, respectively, was found and studied by ¹H NMR spectroscopy.     

The reaction of hypophosphorous acid with chloral

Conclusions The condensation of chloral with hypophosphorous acid has given,,-triebloro--hydroxyethyl phosphonous and bis-(, ,-trichloro--hydroxyethyl)-phosphinic acids.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 6, p. 1095, June, 1966.     

On triazoles. I. The reaction of N-cyanocarbonimidodithioic acid diesters with hydrazines

The reaction of N-cyanocarbonimidodithioic acid di(alkyl and aralkyl)esters with different alkyl-, aralkyl- and arylhydrazines to yield 1-substituted-3-R-thio-5-amino-1H-1,2,4-triazoles ( 3 ) and 2-substituted-3-R-thio-5-amino-2H-1,2,4-triazoles ( 4 ) was studied. Isolation of the different types of isomeric pairs of 3 and 4 helped to prove the structure of products obtained which made possible correction of some confusion in the literature. The 3 (R = H) tautomeric structure of the non-substituted derivatives was supported by comparison of their uv and cmr spectra with those of the alkylated and aralkylated derivatives 3 and 4 , respectively, again correcting confusion in the literature. An hplc determination of the ratio of products 3 and 4 formed in the above reactions with different hydrazines made it possible to prove the mechanism of the reaction.