Reaction of 1-Acetyl-5-hydroxy-2-phenylpyrazolidines with Amino Acid Esters

Reaction of 1-acetyl-2-phenyl-5-hydroxypyrazolidines with amino acid esters occurs to give the corresponding N-pyrazolidinyl amino acids under mild conditions.     

Synthesis and alkylation of 4,6-diphenyl-3-thiocarbamoyl-3,4,5,6-tetrahydropyridine-2(1H)-one and 4,6-diphenyl-3-thiocarbamoyl-3,4-dihydropyridine-2(1H)-one

Alkylation of 3-thiocarbamoyl-3,4,5,6-tetrahydropyridine-2(1H)-one with methyl iodide has given 5-methylthio-2,6-diazabicyclo[2.2.2]oct-5-en-3-one and 3-methyl-thiocarbonyl-3,4-dihydropyridine-2(1H)-one. Alkylation of 3-thiocarbamoyl-3,4-dihydridine-2(1H)-one with iodoacetamide affords 3-(1-amino-1-carbamoyl-3,4-methyl-thiomethylene)-1,4-dihydropyridine-2-one, which in acidic media is converted into 3-(4-oxo-3,5-dihydro-1,3-thiazol-2-ylidene)-1,4-dihydropyridine-2-one.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 787–794, June, 1989.     

Bis(2-alkyl-4-thiocarbamoyl-4-pyridinium) hexafluorosilicates

The reaction of 45% silicahydrofluoric acid with 2-ethyl-4-thiocarbamoyl-4-pyridine (L¹) and 2-propyl-4-thiocarbamoyl-4-pyridine (L²) yields (L¹H)₂SiF₆ and (L₂H)₂SiF₆ hexafluorosilicates. These hexafluorosilicates are characterized by the data of IR spectroscopy, mass spectrometry, potentiometry, and solubility. The structure of (L¹H)₂SiF₆ is determined by X-ray diffraction. In the ionic structure of the complex, the L¹H⁺ cations (the protonation center is the pyridinic N atom) and SiF ₆ ^2? anions (Si-F 1.657(2)–1.699(2) Å) are joined by a system of interionic hydrogen bonds NH?F. Correlation between the characteristics of the interionic hydrogen bonds and the solubility of the hexafluorosilicates is discussed.     

Synthesis of 4-thiocarbamoyl-5-aminopyrazoles

Aryl and t-butylhydrazines react with 2-cyano-3-ethoxythiocrotonamide affording 2-cyano-3-aryl-t-butylhy-drazinothiocrotonamides. These intermediates can be easily cyclized to 4-thiocarbamoyl-5-aminopyrazoles by heating a few minutes in a strong base. Alkylhydrazines react with 2-cyano-3-ethoxythiocrotonamide yielding directly a mixture of the cyclized compounds 4-cyano-5-aminopyrazoles and 4-thiocarbamoyl-5-aminopyr-azoles.     

Cyclization of 1-hydroxy-2-(oxoalkynyl)anthraquinones

Procedures were developed for the heterocyclization of 2-benzoylethynyl-1-hydroxy-and 1-hydroxy-2-(1-oxo-3-phenylpropynyl)anthraquinone. The regioselective preparation of 2-substituted anthra[1,2-b]pyran-4,7,12-triones was demonstrated to be possible under mild conditions.__________Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2686–2692, December, 2004.     

Synthesis of substituted 5-oxo-1-thiocarbamoyl-3-pyrazoline-4-alkanoic acid derivatives

Cyclization of the 4-methyl-3-thiosemicarbazone of diethyl acetylsuccinate (1a) by the action of ammonium hydroxide followed by acidification afforded ethyl 3-methyl-1-methylthiocarbamoyl-5-oxo-3-pyrazoline-4-acetate (11a). Pmr spectral analyses using shift reagent, Eu(fod)₃, in deuteriochloroform indicated the presence also of approximately 15% of a second tautomer, ethyl 5-hydroxy-3-methyl-1-(methylthiocarbamoyl)pyrazole-4-acetate (11a'). 3-Methyl-1-methyl-thiocarbamoyl-5-oxo-pyrazoline-4-acetamide (11b) was prepared by extending the reaction time of 1a with ammonium hydroxide. Alkaline hydrolysis of 11a provided the corresponding acid 3-methyl-1-methylthiocarbamoyl-5-oxo-3-pyrazoline-4-acetie acid (11c). Regeneration of 11a was achieved by the reaction of ethyl 3-methyl-5-oxo-3-pyrazoline-4-acetate (IV) with methyl isothiocyanate. The latter reaction provided confirmation of structure for 11a. The preparation of other pyrazolin-5-ones by cyclization of thiosemicarbazones of ethyl formylsuccinate and ethyl acetylglutarate also is presented. All spectra are in accord with the proposed structures.     

Charge localization in molecule-ions upon electron-impact. Mass spectra of some substituted 1-carbamoyl- and 1-thiocarbamoyl-2-pyrazolines and related compounds

The mass spectra of some substituted 2-pyrazolines and a pyrazolidine are discussed. With the exception of III which favours McLafferty rearrangements prior to fragmentation, I, IV and V fragment to give isocyanate or isothiocyanate radicals and ions with structures corresponding to their heterocyclic molecular compounds. These results which can be explained in the light of the concept of charge localization at preferential sites, are in good agreement with the ionization potential studies on substituted ureas and thioureas.⁵ Other compounds show simple straight-forward fragmentations upon electron-impact.     

Oxidative Cyclization of 2-Arylhydrazonothioacetamides

Intramolecular oxidative cyclization of 2-arylhydrazonothioacetamides was studied, and applicability limits of this reaction for the synthesis of 2-aryl-1,2,3-thiadiazol-5(2H)-imines were determined.     

Cyclization of 1-(pentafluorophenyl)-2- aminoalkanols

The nitro group in 1-(pentafluorophenyl)-2-nitroalkanols is reduced selectively to a hydroxylamino or amino group by controlled potential electrochemical reduction. The pentafluoro-phenylaminoalkanols cyclize readily on heating in dimethylformamide to give homologs of 4,5,6,7-tetrafluoroindole. It is shown that the intermediate in the cyclization of 1-pentafluorophenyl-2-aminoethanol is 3-hydroxy-4,5,6,7-tetrafluoroindoline. Cyclization of 1-pentafluorophenyl-2-hydroxyaminoethanol gave 1,3 -dihydroxy-4,5,6,7-tetrafluoroindoline.Translated from Khimiya Geterotsiklicheskikh Soedinenii, Vol. 6, No. 5, pp. 622–625, May, 1970.     

Cyclization of N1(1-Anthmquinonyl)-N2-phenylthiourea into thiazole derivatives

N¹-(1-Anthraquinonyl)-N²-phenylthiourea, obtained from the reaction of 1-amino-anthraquinone with phenyl isothiocyanate, cyclizes in an alkaline medium into 2-3-dihydro-2-phenylimino-1H-anthra[1,2-d]thiazole-6,11-dione. Treatment of anthraquinonylthiourea with bromine in chloroform results in the formation of 1-(2-benzothiazolyl)aminoanthraquinone together with a small amount of anthrathiazole.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1273–1277, September, 1989.     

Cyclization of 3-Cyclopent-2-Enyl-4-Hydroxy[1]Benzopyran-2-One

Cyclization of 3-cyclopent-2-enyl-4-hydroxy[1]benzopyran-2-one (1) with cold cone. sulfuric acid gave a mixture of two products, 2 (10%) and 3 (80%). However, on treatment with mercuric chloride 1 furnished the linear product 4 in 60% yield while with mercuric acetate the bicyclic product 8 was obtained in 50% yield. The structures of products are established by chemical correlation.     

Phosphole-Fused Dehydropurpurins via Titanium-Mediated [2+2+1] Cyclization Strategy

A [2+2+1] cyclization strategy of bis(alkynyl)porphyrin using low-valent titanium species, generated in situ, afforded phosphole-fused dehydropurpurins for the first time. The systematic investigations on the electronic properties of the dehydropurpurins revealed their unique features owing to the oxidation states of the phosphorus atom on the fused phosphole ring. The phosphole P=O and P=S derivatives were found to possess high electron-accepting character derived from phosphorus(V) centers without the contribution of 24π antiaromatic character, suggesting their potential utility as electron-accepting materials. In contrast, the phosphorus(III) derivatives revealed different optical and electrochemical properties arising from both 18π aromatic and 24π antiaromatic networks including the lone pair of the phosphorus(III) atom. Overall, the oxidation state of the phosphorus atom has a clear impact on the whole electronic properties, demonstrating the advantages of chemical modifications of the phosphorus center for creating an exotic π-system. The application of titanium-mediated [2+2+1] cyclization to porphyrins is highly promising for expanding a world of heterole-fused porphyrinoids.     

Cyclization of 1-arylthiosemicarbazides to benzothiazoles

It is known that 1-arylthiosemicarbazides are cyclized to 2-aminobenzothiazoles in acidic media. This reaction was extended to 1,3- and 1,4-disubstituted thiosemicarbazides. It is shown that the rearrangement proceeds through a step involving the formation of o-aminophenylisothioureas. The reaction conditions and substituents in the benzene ring or attached to the nitrogen atoms of the thiosemicarbazides do not have a substantial effect on the ratio of the resulting 2-amino- and 2-phenyl(methyl)aminobenzothiazoles (11). In the case of m-chlorophenylthiosemicarbazide, 5- and 7-chloro-2-aminobenzothiazoles are obtained in equimolar amounts, whereas the 7 isomer (52) is the major product from m-tolylthiosemicarbazide.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 467–475, April, 1978.     

Cyclization of 1,3-disubstituted 2-(3-butenyl)-2-cyclohexen-1-ols

The cationic cyclization of cyclohexenols 8a-c gave mixtures of the octalinols 9a-c and 10a-c with 9a-c as main products. By cyclization of the isomeric educts 13a-c, the same products were formed in different proportions.     

Cyclization of esters of 1-bromo-2-propanol and 2-bromo-1-propanol by the action of silver trifluoromethanesulfonate

Conclusions The possibility of forming 1,3-dioxalanium cations from various esters of 1-bromo-2- propanol and 2-bromo-1-propanol under conditions for the previously studied isomerization of (I) and (II) was demonstrated.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 3, pp. 723–724, March, 1989.