39856-57-0Relevant academic research and scientific papers
Mild regioselective halogenation of activated pyridines with N-bromosuccinimide
Canibano,Rodriguez,Santos,Sanz-Tejedor,Carreno,Gonzalez,Garcia-Ruano
, p. 2175 - 2179 (2007/10/03)
Regioselective mono and dihalogenations of amino, hydroxy and methoxy pyridines (2-, 3-, and 4-substituted) as well as 2,6-dimethoxy pyridine with N-bromosuccinimide in different solvents have been studied. Reactivity of the substrates decreases in the order amino>hydroxy>methoxy and regioselectivity depends on the position of the substituent (2-substituted > 3-substituted). In most of the cases we obtained monobrominated derivatives regioselectively and in high yields. Hydroxy and amino pyridines can also be dibrominated in almost quantitative yield with 2 equivalents of NBS.
Bromination of Some Pyridine and Diazine N-Oxides
Paudler, William W.,Jovanovic, Misa V.
, p. 1064 - 1069 (2007/10/02)
Selected monosubstituted pyridines, pyrazines, pyrimidines, and their N-oxides, having an electron-donating substituent, were successfully brominated under very mild conditions.The N-oxide function itself is not sufficient to cause these ?-deficient systems to undergo electrophilic aromatic halogenation.Only strongly electron-donating substituents (amino groups) activate the heterocyclic nucleus toward bromination.These substituents direct the electrophilic substitution ortho/para to them with or without the N-oxide group present.Pyridine and diazines with moderately activating substituents such as alkoxy groups are brominated only when their ortho/para activation is augmented by the activation of the N-oxide funtion.Failure to brominate 5-methoxypyrimidine 1-oxide may well reflect the greater ? deficiency of the pyrimidine ring.
