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Synthesis of Mesoionic Triazolo[4,3-α]quinoxalines
Yoshihisa, Kurasawa,Tae, Kawano,Ritsuko, Katoh,Atsushi, Takada,Kim, Ho Sik,Yoshihisa, Okamoto 대구효성가톨릭대학교 자연과학연구소 1992 基礎科學硏究論集 Vol.1992 No.1
The reaction of 6-chloro-2(1-methylhydrazino)quinoxaline 4-oxide 1 or 6-chloro-2-(1-methylhydrazino)-quinoxaline 5 with phenyl isothiocyanate under reflux in N,N-dimethylformamide gave 7-choloro-3-methyl-1,2,4-triazolo[4,3-a]quinoxalin-3-ium-1-thioate 4, which was also obtained by refluxing of 6-chloro-2-[1-methyl-2-(N-phenylthiocarbamoyl)hydrazino]quinoxaline 4-oxide 2b or 6-chloro-2-[1-methyl-2-(N-phenylthiocarbamoyl)hydrazino]quinoxaline 6 in N,N-dimethylformamide.
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.
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.
Yoshihisa, Kurasawa,Kim, Ho Sik,Ritsuko, Katoh,Tae, Kawano,Atsushi, Takada,Yoshihisa, Okamoto 대구효성가톨릭대학교 자연과학연구소 1991 基礎科學硏究論集 Vol.1991 No.1
The reaction of the hydrazones 5a-c with 2-chloroacrylonitrile produced the 1,2-diazepino[3,4-b]quinoxaline hydrochlorides 6a-c, which were transformed into the 5,6,7,13-tetrahydro-5,14-methano-16-oxo-1,5,6-benzoxadiazonino[3,4-b]quinoxalines 7a-c, respectively. The oxidation of 7a-c with diethyl azodicarboxylate afforded the 7,13-dihydro-5,14-methano-16-oxo-1,5,6-benzoxadiazonino[3,4-b]quinoxalines 8a-c, respectively. Compounds 7a-c and 8a-c were also obtained by a one-pot synthesis from 5a-c and 6a-c, respectively.
Yoshihisa, Kurasawa,Noriko, Yoshishiba,Tomomi, Kureyama,Tomoko, Okano,Atsushi, Takada,Kim, Ho Sik,Yoshihisa, Okamoto 대구효성가톨릭대학교 자연과학연구소 1992 基礎科學硏究論集 Vol.1992 No.1
The reaction of 6-chloro-2-hydrazinoquinoxaline 4-oxide 5 with thriethyl orthoformate gave 7-chloro-1,2,4-triazolo[4,3-a]quinoxaline 5-oxide 6. The reaction of compound 6 with phenyl isocyanate afforded 7-chloro-4-phenylamino-1,2,4-triazolo[4,3-a]quinoxaline 7, while the reaction of compound 6 with phenyl isothiocyanate resulted in deoxygenation to provide 7-chloro-1,2,4-triazolo[4,3-a]quinoxaline 8. However, the reaction of compound 6 with allyl isothiocyanate effected the 1,3-dipolar cycloaddition reaction, but not deoxygenation, to furnish 9-chloro-4,5-dihydroisoxazolo[2,3-a][1,2,4]triazolo[3,4-c]quinoxaline-5-ylmethylisothiocyanate 9. Moreover, the reduction of compound 9 with iron/acetic acid resulted in ring transformation to give 11-chloro-7-hydroxy-4-thioxo-4,5,6,7,8,9-hexahydro-1,2,4-triazolo[4,3,2-o,p][1,3]diazocino[4,5-b]quinoxaline 10, whose acetylation afforded 5-acetyl-11-chloro-7-hydroxy-4-thioxo-4,5,6,7,8,9-hexahydro-1,2,4-triazolo[4,3,2-o,p][1,3]diazocino[4,5-b]quinoxaline 11.
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.