Keisuke Katou

A new synthesis of 2,12-dithia[3.3](1,4)cycl[3.2.2.] azinophanes

2,12-Dithia[3.3](1,4)cycl[3.2.2]azinophanes which were the key intermediates for the syntheses of [2.2](1,4)-cycl[3.2.2]azinophanes were synthesized by the reaction of bis(mercaptomethyl)cyclazine and dihalogenated compounds (2,6-lutidine dibromide) with Cs 2 CO 3 in N,N-dimethylformamide (DMF)

A novel 1,6-cyclization of imidazolium N-allylides (2) : formation of the mesomeric betaine, 7-iminoimidazo[1,2-a]pyridiniumide

Treatment of imidazolium N-allylide (3) in refluxing 1,2,4-trimethylbenzene resulted in 1,6-cyclization to give the mesomeric betaine, 7-iminoimidazo [1,2-a] pyridiniumide (4). On the other hand, heating of 1-cyanoimidoylmethylimidazolium N-ylide (6) in refluxing 1,2,4-trimethyl-benzene underwent 1,6-cyclization and debenzylation to give 8-amino-imidazo [1,2-a] pyrazine (7). Furthermore, treatment of the imidazolium salt (1a) and ethyl ethoxymethylenenitroacetate (2d) with K 2 CO 3 in DMSO afforded the mesomeric betaine, imidazo [1,2-a] pyridiniumide (12), whereas the reaction of 1a and nitroketene dithioacetal (2e) with K 2 CO 3 in DMSO resulted in 1,5-dipolar cyclization to produce pyrrolo [1,2-a] imidazole (13) and pyrrolo [1,2-a] pyrazine (14)

Novel synthesis of methine dyes absorbing in the near-infrared region

Abstract By reaction of 2-(1-cyano-1-methylthio)methyleneindan-1,3-dione ( 2 ) with nucleophiles, the corresponding substituted compounds ( 10–16 ) as typical donor-acceptor chromogens were obtained. Novel methine dyes ( 24,25 ) absorbing in the near-IR region (650–850 nm) were synthesized by condensation of 16 and malononitrile with TiCl 4 and pyridine.

Synthesis of Imidazo [1,2-a] pyridine Derivatives and Their Reactions

By the reaction of 2-benzoylmethylimidazoles (1a, b) with polarized olefins (2, 3) in the presence of K2CO3, the corresponding imidazo[1,2-a]pyridine derivatives (4, 5) were obtained. Methylsulfinylimidazopyridine derivative (7) obtained by the reaction of 5b with m-chloroperbenzoic acid (m-CPBA), easily underwent nucleophilic substitution to give the corresponding substituted compounds (8a--e). The substitution of chloroimidazopyridine derivative (11) with nucleophiles produced the corresponding substituted compounds (12a--d).