275-68-3Relevant academic research and scientific papers
On the Reaction of N-Vinyliminophosphoranes. Part 7. A Short New 1-Aza-azulene Synthesis
Nitta, Makoto,Iino, Yukio,Hara, Eijiro,Kobayashi, Tomoshige
, p. 51 - 56 (2007/10/02)
Thermal reaction of triphenyl(vinylimino)phosphorane derivatives with several tropones have been studied to provide a short new route to the 1-aza-azulene ring system. (1-Phenylvinylimino)-, vinylimino-, and a mixture of (1-butylvinylimino)- and (1-methylpent-1-enylimino)-triphenylphosphorane were treated with tropone and alkylated tropones in an enamine alkylation process, and the subsequent aza-Wittig reaction resulted in the formation of 1,8-dihydrocycloheptapyrroles.The pyrrole derivatives were easily dehydrogenated by nickel peroxide or manganese dioxide to give 1-aza-azulene derivatives.In a similar fashion, the iminophosphoranes were treated with 2-bromotropone or with 2-chlorotropone in the presence of triethylamine to give 1-aza-azulenes in a single step.The 1-aza-azulenes, which were halogenated on the seven-membered ring, were also prepared conveniently by the reaction of triphenyl(1-phenylvinylimino)phosphorane with 2,7-dibromo-, 2,4,7-tribromo-, and 2,3,5,7-tetrachlorotropone, albeit in modest yields.
