The reaction of triethylamine with bromine. An evaluation of the formation constant of the transient 1:1 complex and a study of its conversion into products.

✍ Scribed by G. Bellucci; G. Berti; R. Bianchini; L. Orsini

• Publisher: Elsevier Science
• Year: 1982
• Tongue: French
• Weight: 258 KB
• Volume: 23
• Category: Article
• ISSN: 0040-4039
• DOI: 10.1016/s0040-4039(00)87692-3

✦ Synopsis

Triethylamine and bromine in 1,2-dichloroethane give a non isolable 1:l charge trans- fer complex with Kf>10 7 -1 M , which undergoes a fast intramolecular oxidation-reduction to N,N- -diethylethylideneiminium bromide and hydrogen bromide. The formation of optically active dibromides from prochiral or racemic alkenes and Cinchona alkaloids/Br2 1:l complexes has been reported.' The detailed mechanism, and in particular the site of halogen complexation, either the quinoline or the quinuclidine N of the alkaloid, has however not been clarified, although the latter, being chiral itself and close to chiral carbons, is most probably the one involved in the asymmetric catalysis. Whereas it has been unambiguously demonstrated2 that pyridine/Br2 charge transfer complexes can act as direct sources of electrophilic bromine, no definite evidence for tertiary aliphatic amine complexes of Br2 acting as brominating agents has been produced so far. In order to clear up these points and give a further