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Please login or sign up for a free trial to access the full content. Variation 9: Bromination with Bromine Donors: Perfluoroalkanesulfonyl Bromides or Benzeneselenenyl Bromide

DOI: 10.1055/sos-SD-026-00761

Suffert, J.Science of Synthesis, (200526915.

Bromine donors such as benzeneselenenyl bromide or perfluorinated alkylsulfonyl bromides can be used to selectively brominate 3-oxo steroids,[‌145‌] cyclic ketones, enamines, or enol trimethylsilyl ethers.[‌146‌] An example of kinetic versus thermodynamic control is noted when 5β-androstane-3,17-dione is reacted with benzeneselenenyl bromide. After 1 hour only 4β-bromo-5β-androstane-3,17-dione (144) is isolated in 65% yield; however, increasing the reaction time to 96hours, which does not change significantly the overall yield, gives a 1:5 ratio (by NMR) of 4β-bromo-5β-androstane-3,17-dione (144) and the 2β-bromo isomer 145 (Scheme 64).

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