A short route to 3-alkynyl-4-bromo(chloro)cinnolines by Richter-type cyclization of ortho-(dodeca-1,3-diynyl)aryltriaz-1-enes |
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Authors: | Olga V Vinogradova |
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Institution: | Saint-Petersburg State University, 26 Universitetskij pr., Petrhoff, St. Petersburg, 198504, Russia |
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Abstract: | 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: furo3,2-c]cinnoline and cinnolinone. Substitution of bromine in 3-(alk-1-ynyl)-4-bromocinnolines is achieved with methylamine, Na2S and ethynylbenzene affording pyrrolo3,2-c]cinnoline, thieno3,2-c]cinnoline and 3,4-diethynylcinnoline, respectively. |
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Keywords: | ortho-(Alka-1 3-diynyl)aryltriazenes ortho-(Alka-1 3-diynyl)arenediazonium salts Richter cyclization 3-Alkynyl-4-halocinnolines Synthesis: pyrrolo[3 2-c]cinnolines thieno[3 2-c]cinnoline 3 4-diethynylcinnoline |
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