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Kurasawa, Yoshihisa,Hosaka, Tomoyoshi,Ikeda, Kazue,Matsumoto, Yuko,Ishikura, Aiko,Takada, Atsushi,Kim, Ho Sik,Okamoto, Yoshihisa 대구효성가톨릭대학교 자연과학연구소 1994 基礎科學硏究論集 Vol.1994 No.1
The 3-(arylhydrazono)methyl-2-oxo-1,2-dihydroquinoxalines 9-11 were synthesized by the reaction of the quinoxalines 6-8 with various p-substituted benzenediazonium salts. Compounds 9-11 showed the tau-tomeric equilibria between the hydrazone imine A and diazenyl enamine B forms in dimethyl sulfoxide media. The substituent effect on the tautomer ratios of A to B was studied by the nmr spectroscopy to clar-ify that the presence of the ester group R^2 on the hydrazone carbon and electron-donating p-substituent R^1 on the side chain benzene ring exhibited a tendency to increase the ratios of the tautomer A.
Kurasawa, Yoshihisa,Hosaka, Tomoyoshi,Takada, Atsushi,Kim, Ho Sik,Okamoto, Yoshihisa 대구효성가톨릭대학교 자연과학연구소 1994 基礎科學硏究論集 Vol.1994 No.1
The 3-(arylhydrazono)methyl-2-oxo-1,2-dihydroquinoxalines 1a-e and 2a-ishowed tautomeric equilib-ria between the hydrazone imine A and diazenyl enamine B forms in dimethyl sulfoxide media. The sub-stituent effects on the tautomer ratios of A to B in compounds 1a-e and 2a-i were studied by the nmr spec-troscopy. The electron-donating or electron-withdrawing p-substituents R^1 in compounds 2a-i representeda tendency to increase the ratios of the tautomer A or the tautomer B. respectively, exhibiting the linearcorrelation of the Hammett constants δ_p (-0.17 to +078) with the tautomer ratios of A to B or the tau-tomeric equilibrium constants K_T. However, the presence of the ester group R^2 in compounds 1a-e induced the exclusive existence of the tautomer A regardless of the nature of the p-substituent R^1. In the tautomeric thermodynamic study, the elevating temperature increased the ratios of the hydrazone imine tautomer A in compounds 2a-i. The tautomeric thermodynamic parameters △G˚, △H˚ and △S˚were derived from the van't Hoff plots for compounds 2a,b,h,i, wherein the entropy term dominated the free-energy difference between the A and B tautomers.
Kurasawa, Yoshihisa,Kureyama, Tomomi,Yoshishiba, Noriko,Kathoh, Ritsuko,Takada, Atsushi,Kim, Ho Sik,Okamoto, Yoshihisa 대구효성가톨릭대학교 자연과학연구소 1993 基礎科學硏究論集 Vol.1993 No.1
The reaction of 6-chloro-2-(l-methylhydrazino)quinoxaline 4-oxide 8 with furfural, 3-methyl-2-thiophene-carbaldehyde, 2-pyrrolecarbaldehyde, 4-pyridinecarbaldehyde and pyridoxal hydrochloride gave 6-chloro-2-[2-(2-furylmethylene)-l-methylhydrazino]quinoxaline 4-oxide 5a, 6-chloro-2-[1-methyl-2-(3-methyl-2-thienyl-methylene)hydrazino]quinoxaline 4-oxide 5b, 6-chloro-2-[1-methyl-2-(2-pyrrolylmethylene)hydrazino]quinoxaline 4-oxide 5c, 6-chloro-2-[1-methyl-2-(4-pyridylmethylene)hydrazino]qunoxaline 4-oxide 5d and 6-chloro-2-[2-(3-hydroxy-5-hydroxymethyl-2-methyl-4-pyridylmethylene)-1-methylhydrazino]quinoxaline 4-oxide 5e, respectively. The reaction of compound 5a or 5b with 2-chloroacrylonitrile afforded 8-chloro-3-(2-furyl)-4-hydroxy-1-methyl-2,3-dihydro-1H-1,2-diazepino[3,4-b]quinoxaline-5-carbonitrile 6b, respectively, while the reaction of compound 5e with 2-chloroacrylonitrile furnished 11-chloro-7,13-dihydro-4-hydroxy-methyl-5,14-methano-1,7-dimethyl-16-oxopyrido[3',4':9,8][1,5,6]oxadiazonino[3,4-b]quinoxaline 7.
Reaction of Azole Condensed Quinoxaline N-Oxides with Acetic Anhydride
Kurasawa, Yoshihisa,Hosaka, Tomoyoshi,Matsumoto, Yuko,Ishikura, Aiko,Ikeda, Kazue,Takada, Atsushi,Kim, Ho Sik,Okamoto, Yoshihisa 대구효성가톨릭대학교 자연과학연구소 1994 基礎科學硏究論集 Vol.1994 No.1
The reaction of 7-chlorotetrazolo[1,5-a]quinoxaline 5-oxide 6a with acetic anhydride gave 7-chloro-5-(7-chlorotetrazolo[1,5-a]quinoxalin-4-yl)-4,5-dihydro-4-oxotetrazolo[1,5-a]quinoxaline 7a, while the reaction of 7-chloro-1,2,4-triazolo[4,3-a]quinoxaline 5-oxide 6b with acetic anhydride afforded 7-chloro-5-(7-chloro-1,2,4-triazolo[4,3-a]quinoxalin-4-yl)-4,5-dihydro-4-oxo-1,2,4-triazolo[4,3-a]quinoxaline 7b and 7-chloro-4,5-dihydro-4-oxo-1,2,4-triazolo[4,3-a]quinoxaline 8b. The reaction of compound 6a or 6b with acetic anhydride/acetic acid provided 7-chloro-4,5-dihydro-4-oxo-tetrazolo[1,5-a]quinoxaline 8a or compound 8b, respectively.
Kurasawa, Yoshihisa,Kureyama, Tomomi,Yoshishiba, Noriko,Okano, Tomoko,Takada, Atsushi,Kim, Ho Sik,Okamoto, Yoshihisa 대구효성가톨릭대학교 자연과학연구소 1993 基礎科學硏究論集 Vol.1993 No.1
The reaction of 7-chlorotetrazolo[1,5-a]quinoxaline 50oxide 4a or 7-chloro-1,2,4-triazolo[4,3-a]quinoxaline 5-oxide 4b with 2-chloroacrylonitrile gave 7-chloro-4-(2-cyano-2-hydroxyvinyl)tetrazole[1,5-a]quinoxaline 5a or 7-chloro-4-(2-cyano-2-hydroxyvinyl)-1,2,4-triazolo[4,3-a]uinoxaline 5b, respectively. Alcoholysis of com-pound 5a or 5b afforded 7-chloro-4-ethoxycarbonylmethylene-4,5-dihydrotetrazolo[1,5-a]quinoxaline 6a or 7-chloro-4-ethoxycarbonylmethylene-4,5-dihydro-1.2.4-triazolo[4,3-a]quinoxaline 6b, respectively. Compounds 5a,b were found to exist as a syn and anti mixture of the enol form, while compounds 6a,b occurred as the enamine and methylene imine forms. The tautomeric character and/or D-H exchange of the vinyl protons are described for compounds 5a,b and 6a,b.
Kurasawa, Yoshihisa,Ishikura, Aiko,Ikeda, Kazue,Hosaka, Tomoyoshi,Matsumoto, Yuko,Takada, Atsushi,Kim, Ho Sik,Okamoto, Yoshihisa 대구효성가톨릭대학교 자연과학연구소 1994 基礎科學硏究論集 Vol.1994 No.1
The reaction of 7-chloro-4-ethoxycarbonylmethylene-4,5-dihydro-1,2,4-triazolo[4,3-a]quinoxaline 6 with 4-ethoxycarbonyl-1-methyl-1H-pyrazole-5-diazonium chloride or 4-cyano-1,3-dimethyl-1H-pyra-zole-5-diazonium chloride gave 7-chloro-4-[α-(4-ethoxycarbonyl-1-methyl-1H-pyrazol-5-ylhydrazono)-ethoxycarbonylmethyl]-1,2,4-triazolo[4,3-α]quinoxaline 8a or 7-chloro-4-[α-(4-cyano-1,3-dimethyl-1H-pyrazol-5-ylhydrazono)ethoxycarbonylmethyl]-1,2,4-triazolo[4,3-α]quinoxaline 8b, respectively, while thereaction of 7-chloro-4-ethoxycarbonylmethylene-4,5-dihydrotetrazolo[1,5-α]quinoxaline 7 with 4-ethoxy-carbonyl-1-methyl-1H-pyrazole-5-diazonium chloride or 4-cyano-1,3-dimethyl-1H-pyrazole-5-diazoniumrhloride provided 7-chloro-4-[α-(4-ethoxycarbonyl-1-methyl-1H-pyrazol-5-ylhydrazono)ethoxy-carbonylmethyl]tetrazolo[1,5-α]quinoxaline 9a or 7-chloro-4-[α-(4-cyano-1,3-dimethyl-lH-pyrazol-5-ylhydrazone)ethoxycarbonylmethyl] tetrazolol[1.5-α]quinoxailne 9b, respectively. Compounds 8a,b and 9a,b showed the tautomeric equilibria between the hydrazone imine C and diazenyl enaminc D forms indimethyl sulfoxide and/or trifluoroacetic acid. and the effects of solvent and temperature on the tautomerratios of C to D were studied by the nmr measurements in a series of mixed trifluoroacetic acid/dimethylsulfoxide media (compounds 8a,b and 9a,b) and at various temperatures (compounds 8a,b).
Kurasawa, Yoshihisa,Matsumoto, Yuko,Ishikura, Aiko,Ikeda, Kazue,Hosaka, Tomoyoshi,Takada, Atsushi,Kim, Ho Sik,Okamoto, Yoshihisa 대구효성가톨릭대학교 자연과학연구소 1993 基礎科學硏究論集 Vol.1993 No.1
The reaction of 7-chloro-4-(2-cyano-2-hydroxyvinyl)tetrazolo[1,5-a]quinoxaline 2a with 4-aminopyridine, p-toluidine or p-aminopehnol gave 7-chloro-4-(4-pyridylcarbamoylmethylene)-4,5-dihydrotetrazolo[1,5-a]-quinoxaline 7a, 7-chloro-4-(p-tolylcarbamoylmethylene)-4,5-dihydrotetrazolo[1,5-a]quinoxaline 8a or 7-chloro-4-(p-hydroxyphenylcarbamolymethylene)4,5-dihydrotetrazolo[1,5-a]quinoxaline 9a, respectively. The reac-tion of 7-chloro-4-(2-cyano-2-hydroxyvinyl)-1,2,4-triazolo[4,3-a]quinoxaline 2b with 4-aminopyridine, p-toluidine or p-aminophenol afforded 7-chloro-4-(p-tolylcarbamoylmethylene)-4,5-dihydro-1,2,4-triazolo[4,3-a]quinoxaline 8b or 7-chloro-4-(p-hydroxyphenylcarbamoylmethylene)-4,5-dihydro-1,2,4-triazolo[4,3-a]quinoxaline 9b, respec-tively. The reaction of compound 2a with 2-aminopyridine or 3-aminopyridine provided 7-chloro-4-(2-pyridyl-carbamoylmethylene)-4,5-dihydrotetrazolo[1,5-a]quinoxaline 10 or 7-chloro-4-(3-pyridylcarbamoylmethylene)-4,5-dihydrotetrazolo[1,5-a]quinoxaline 11, respectively. Compounds 7a,b(4-pyridylcarbamoyl)predominated as the enamine tautomer A in a trifluoroacetic acid solution, while compounds 8a,b(p-tolylcarbamoyl)and compounds 9a,b(p-hydroxyphenylcarbamoyl)coexisted as the enamine A and methylene imine B tautomers in a trifluoroacetic acid solution. Moreover, the ratio of the enamine tautomer A elevated in an order of com-pound 11(s-pyridylcarbamoyl), compound 10 (2-pyridylcarbamoyl)and compound 7a (4-pyridylcarbamoyl), reflecting an order of the increase in the pKa values of the aminopyridine side chain moieties. In general, the ratio of the enamine tautomer A was higher in the basic carbamoyl derivatives 7-11 than in the neutral ester derivatives 3a,b. From these results, the basic side chain moiety of the tetrazolo[1,5-a]quinoxalines 7a-11 or 1,2,4-triazolo[4,3-a]quinoxalines 7b-9b was found to increase the ratio of the enamine tautomer A in trifluo-roacetic acid media.
Reaction of Enol Type Acyl Cyanide with o-Aminophenol
Kurasawa, Yoshihisa,Yoshishiba, Noriko,Kureyama, Tomomi,Takada, Atsushi,Kim, Ho Sik,Okamoto, Yoshihisa 대구효성가톨릭대학교 자연과학연구소 1993 基礎科學硏究論集 Vol.1993 No.1
The reaction of 7-chloro-4-(2-cyano-2-hydroxyvinyl)tetrazolo[1,5-a]quinoxaline 2a with o-aminophenol gave 7-chloro-4-(b-hydroxyphenylcarbamoylmethylene)-4,5-dihydrotetrazolo[1,5-a]quinoxaline 4, while the reaction of compound 2a with o-aminophenol hydrochloride afforded 4-[2-(2benzoxazolyl)-2-hydroxyvinyl]-7-chloro-tetrazolo[1,5-a]quinoxaline 5, whose acetylation provided 4-[2-acetoxy-2-(2-benezoxazolyl)vinyl]-7-chlorotetra-zolo[1,5-a]quinoxaline 6. The behavior in a deuteriodimethyl sulfoxide or deuteriotrifluoroacetic acid solu-tion is described for compounds 4-6.
Tautomeric Structure of 1-Methyldihydropyridazino[3,4-b]quinoxalines in Solution
Kurasawa, Yoshihisa,Takada, Atsushi,Kim, Ho Sik,Okamoto, Yoshihisa 대구효성가톨릭대학교 자연과학연구소 1993 基礎科學硏究論集 Vol.1993 No.1
The reaction of 6-chloro-2-(1-methylhydrazino)quinoxaline 4-oxide 1 with ethyl 2-ethoxymethylene-2-cyano-acetate or ethoxymethylenemalononitrile gave 6-chloro-2-[2-{2-cyano-2-ethoxycarbonylvinyl)-1-methylhy-drazino]quinoxaline 4-oxide 3a or 6-chloro-2-[2-(2,2-dicyanovinyl)-1-methylhydrazino]quinoxaline 3b, respec-tively. The reaction of 3a with a base afforded 7-chloro-1-methyl-1,5-dihydropyridazino[3,4-b]quinoxaline 4. From the NOE spectral data, the 1-methyldihydropyridazino[3,4-b]quinoxalines 2a,2b and 4 were found to exist as the 1,5-dihydro from in a dimethyl sulfoxide or trifluoroacetic acid/dimethyl sulfoxide solution.