Practically carrier-free labelling of aromatic compounds with bromine-77 via N-chloro-tetrafluorosuccinimide
✍ Scribed by H. H. Coenen; H.-J. Machulla; G. Stöcklin
- Book ID
- 102900904
- Publisher
- John Wiley and Sons
- Year
- 1979
- Tongue
- French
- Weight
- 524 KB
- Volume
- 16
- Category
- Article
- ISSN
- 0022-2135
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✦ Synopsis
A new method for practically carrier-free aromatic bromination has been developed using N-chloro-tetrafluorosuccinimide (NCTFS) and bromide-77. The optimum bromination conditions have been determined using toluene as a model system. In trifluoroacetic anhydride (TFA) , which proved to be the best solvent, a "one-pot'' synthesis with carrierfree bromide-77 gives rise to a 52 % radiochemical yield of bromotoluenes. No benzylbromide is formed. At room temperature the reaction is completed within about 30 min, the highest yields being obtained at NCTFS-concentrations of 2mole/l. In pure anhydride (TFA) the chlorinating side-reaction of NCTFS does not take place. The reactivity towards simple benzene derivatives (C6H5X, X = OCH3, CH3, H, F, Br, NO2) is strongly dependent on the activation of the aromatic ring. A high ortho-and particularly para-selectivity is observed, and an electrophilic substitution process via ionic species is discussed.