84499-34-3Relevant academic research and scientific papers
Base-Catalyzed Rearrangement of N-(Aryloxy)pyridinium Salts. Effect of a 3-Substituent in the Pyridine Ring upon Orientation. Synthesis of Novel Tricyclic Rings
Abramovitch, Rudolph A.,Inbasekaran, Muthiah N.,Kato, Shozo,Radzikowska, Teresa A.,Tomasik, Piotr
, p. 690 - 695 (1983)
The orientation in the base-catalyzed rearrangement of 3-substituted N-(aryloxy)pyridinium tetrafluoroborates (5) to 2- or 6-(2-hydroxyaryl)pyridines has been studied.A 3-methyl group directs exclusively to the 6-position while inductively electron-withdrawing substituents (Cl, Br, I, OMe, CO2Me, COMe) direct mainly, if not exclusively, to C-2.The phenols derived from 3-CO2Me derivates cyclize spontaneously to the substituted pyridocoumarins (8) in useful yields, and that from the 3-COMe compound gives 10-hydroxy-10-methyl-6-nitropyridobenzopyran (9).The 3-halo-2-(2-hydroxyaryl)pyridines cyclize to benzofuropyridines(10,15) on heating with potassium hydroxide and copper powder.Authentic benzofuropyridine (12) is obtained by the Pschorr ring closure of the diazonium salt of 3-(o-aminophenoxy)pyridine (14).The substituent effects are explained mainly on the basis of the inductive effect of the substituent: steric effects play a slight role.A minor side reaction is thought to involve the intermediacy of free radicals.
Pyridine N-Sulfides. Benzisothiazolopyridinium Tetrafluoroborates and Benzothiophenopyridines. Novel Heterocyclic Systems
Abramovitch, Rudolph A.,Inbasekaran, Muthiah N.,Miller, Adrian L.,Hanna, James M.
, p. 509 - 512 (2007/10/02)
2-(2-Mercaptophenyl)pyridines are prepared from the corresponding phenols and oxidized with N-chlorosuccinimide and silver tetrafluoroborate to benzisothiazolopyridine salts (4).The latter do not rearrange thermally or photochemically to benzothiophenopyridines (19) and are attacked by nucleophiles at sulfur rather than in the pyridine ring, to give the original 2-(2-mercaptophenyl)pyridine back in a reaction involving a dismutation. 19 is prepared by rearranging O-dimethylthiocarbamate to the S-aryl compound and heating the latter with strong base.
