Study of Cyclyzation of o-(1-Alkynyl)- and o-(1,3-Butadiynyl)aryltriazenes Under the Action of Acids

By the methods of NMR and ESI MS (Electrospray Ionization Mass Spectrometry) the investigation was carried out of Richter cyclization of o-(1-alkynyl)- and o-(1,3-butadiynyl)arenediazonium salts generated by acid cleavage of triazenes. The effect was shown of the substituents at the carbon atom of the triple bond and in the aromatic ring, of the solvent, temperature, and the reagents ratio on the rate of the cyclization and the yield of its products, 4-bromo-3-alkyl- and 4-bromo-3-ethynylcinnolines; the conditions of their synthesis were optimized. The possibility to use 4-bromo-3-ethynylcinnolines as substrates of electrophilic cyclization was demonstrated.