Navigation

0 Hits

  • Previous / Next

You are using Science Of Synthesis as a Guest.
Please login or sign up for a free trial to access the full content.
26.6.3.1.1.9 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).

Meeeee 88 α-Meeeeeeeeee ee 8-Mee Meeeeeee eeee Meeeeeeeeeeeeeee Meeeeee[‌888‌]

Meeeeeeeeeeeeeeeeeeeeee eeeeeeee (MMMM8Me) eee eeeeeeee eeee eee eeeeeeeeeeeee eeeeee eeeeeeeeeeeeeeeeeeeeeeee ee eee eeeeee ee eeeeeee ee eeeeee eeeeeeeeeeeee.[‌888‌] Meee eee eeee eeeeeeeeeee eeeeee eeee eeeee eeeeeee eeee eeeeee eeeeeee 888 ee eeee eee eeeeeeeeeeeee α-eeeee eeeeeeeeeee 888 ee eeee ee eeeeeeeee eeeeee eeeeeee eeeeeeeeee eeeeeeeee ee eeeee eeee (Meeeee 88).[‌888‌] Meeeeee, ee e eeeeeeee eeee eeeeeee e eeeeeee ee eeeeeeeeeeeeee eeeeeeeeeee eee eeeeeeeee eeeeeee ee eeeeee eeee eeeeee eeeeeeeee eeeeeee ee eeeeeeeee eee eeeeeeee. Meeeeee eee eeeeeeeeeeeeee eeee eeeeee eeee eeeee eeee eeeee eeeeeeee ee eeee eee eeeeeeeeeeeee α-eeeee eeeeeee.

Meeeee 88 α-Meeeeeeeeee ee Meeeeee eeee Meeeeeeeeeeeeeeeeeeeeee Meeeeeee[‌888‌]

Meeeeeeeeeee Meeeeeeee

8β-Meeee-8β-eeeeeeeeee-8,88-eeeee (888):[‌888‌]

MeMeMe (888ee, 88.8eeee) eee eeeee 8β-eeeeeeeeee-8,88-eeeee (888ee, 88.8eeee) ee MeMMe (88eM). Mee eeeeeee eee eeee ee ee eee 8e eeeeee eeeee eeee eee eeeee eeeeeeee eeeeeeeeeeee eee. Me eee eeeeeeeee eee eeeeeeeeeeeeee (eeeeeee/eeeeee). Meeeeeeeeee MMM eeeee eeee ee eeee eee eeeeeeeeeeee; eeeee: 88%; ee 888888°M.

8β-Meeee-8β-eeeeeeeeee-8,88-eeeee (888):[‌888‌]

Mee eeeeeeee eeeeeeeeee eeee eeeeeeeeeee eeeeeee ee eeeee eeee ee eee eeeeeeee eeeeeeeeeeee eeeeeeeee eeeeee eee eeee eee eeeeeeeee eeee 8 ee 88e, eeee eeeeeeee ee eee eeeeeeeee ee e eeeeeee ee eee eeeeeee 888 eee 888 ee e eeeee 8:8 eeeee ee MMM eeeeeeee. Meeeeeeeeeeeeee ee eee eeeee eeeeeee (eeeeeee/eeeeee) eeee eee eeeee eeeeeeee; eeeee: 88%; ee 888888°M.

Meeee Meeeeee 888 ee Meeeee Meeeeeeeeee eeee Meeeeeeeeeeeeeeeeeeeeee Meeeeeee; Meeeeee Meeeeeeee:[‌888‌]

Mee eeeeeeeeeeeeeeeeeeeeeee eeeeeee eee eeeee eeee ee eeeeeeeee eeeeee ee eee ­eeeeee ee MMe8 (MMMMMMM: eeeee) ee 888°M. Meee eee eeeeeeee eee eeee (eeeeeeeee ee 88M MMM), M8M eee eeeee, eee eeee eee eeeeeeeee eeee eeeeeeeee eeeee, eee eee eeeeeee eeeee eee eeeee (Me8MM8). Meeee eeeeeee ee eee eeeeeee, eeeeeeeeeeee ee eee eeeeeee eeeee eeeeeee eeeeeeee eeee eee eeeeeeeeee eeeeee.

References