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Practically carrier‐free labelling of aromatic compounds with bromine‐77 via N‐chloro‐tetrafluorosuccinimide
Author(s) -
Coenen H. H.,
Machulla H.J.,
Stöcklin G.
Publication year - 1979
Publication title -
journal of labelled compounds and radiopharmaceuticals
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.432
H-Index - 47
eISSN - 1099-1344
pISSN - 0362-4803
DOI - 10.1002/jlcr.2580160612
Subject(s) - chemistry , halogenation , bromine , toluene , trifluoroacetic anhydride , trifluoroacetic acid , succinimide , electrophilic aromatic substitution , bromide , electrophilic substitution , yield (engineering) , benzene , medicinal chemistry , organic chemistry , electrophile , reactivity (psychology) , solvent , ionic liquid , catalysis , medicine , materials science , alternative medicine , pathology , metallurgy
A new method for practically carrier‐free aromatic bromination has been developed using N‐chloro‐tetrafluoro‐succinimide (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 2 · 10 −2 mole/1. In pure anhydride (TFA) the chlorinating side‐reaction of NCTFS does not take place. The reactivity towards simple benzene derivatives (C 6 H 5 X, X = OCH 3 , CH 3 , H, F, Br, NO 2 ) 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.