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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,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,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 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.