A short route to 3-alkynyl-4-bromo(chloro)cinnolines by Richter-type cyclization of ortho-(dodeca-1,3-diynyl)aryltriaz-1-enes
✍ Scribed by Olga V. Vinogradova; Viktor N. Sorokoumov; Irina A. Balova
- Publisher
- Elsevier Science
- Year
- 2009
- Tongue
- French
- Weight
- 289 KB
- Volume
- 50
- Category
- Article
- ISSN
- 0040-4039
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✦ Synopsis
cyclization 3-Alkynyl-4-halocinnolines Synthesis: pyrrolo[3,2-c]cinnolines, thieno[3,2-c]cinnoline, 3,4diethynylcinnoline a b s t r a c t Cleavage of ortho-(dodeca-1,3-diynyl)triazenes in HCl or HBr medium and subsequent cyclization of the resulting diazonium salts is investigated. In the absence of a strong electron-withdrawing substituent, the reaction affords 3-alkynyl-4-bromo(chloro)cinnolines as the only product. A methoxycarbonyl group promotes hydrolysis of 4-halocinnolines which results in the formation of by-products: furo[3,2-c]cinnoline and cinnolinone. Substitution of bromine in 3-(alk-1-ynyl)-4-bromocinnolines is achieved with methylamine, Na 2 S and ethynylbenzene affording pyrrolo[3,2-c]cinnoline, thieno[3,2-c]cinnoline and 3,4-diethynylcinnoline, respectively.