MilliporeSigma

Electrochemical bromination of cholest-5-enes.

Steroids (2005-07-26)
Smiljka S Milisavljević, Klaus Wurst, Gerhard Laus, Mirjana D Vukićević, Rastko D Vukićević
ABSTRACT

Four 5,6-unsaturated steroids--3beta-chlorocholest-5-ene (1a), cholesterol (1b) and its acetate (1c) and benzoate (1d)-were subjected to constant current electrolysis (50 mA, 2 F mol(-1)) in an electrolytic cell divided by a ceramic membrane, using a platinum foil as the anode and a graphite stick as the cathode. When electrolysis was carried out in a solution of tetraethylammonium bromide in aprotic solvents (dichloromethane, acetonitrile or acetic anhydride), the addition of electrochemically-generated elemental bromine onto the double bond of the cholesterol derivatives gave their corresponding 5alpha,6beta-dibromosteroids--3beta-chloro-5alpha,6beta-dibromocholestane (2a), 5alpha,6beta-dibromocholestan-3beta-ol (2b), 5alpha,6beta-dibromocholestan-3beta-yl acetate (2c) and 5alpha,6beta-dibromocholestan-3beta-yl benzoate (2d)--as the sole products, and in good yields (58-91%). However, the electrolysis of steroids 1a-c in a solution of tetraethylammonium bromide with methanol as the solvent proceeded to give, in addition to dibromides 2a-c, the corresponding diastereomeric pairs of 5-bromo-6-methoxysteroids: 5alpha-bromo-3beta-chloro-6beta-methoxycholestane (3a) and 5beta-bromo-3beta-chloro-6alpha-methoxycholestane (4a), 5alpha-bromo-6beta-methoxycholestan-3beta-ol (3b) and 5beta-bromo-6alpha-methoxycholestan-3beta-ol (4b) and 5alpha-bromo-6beta-methoxycholestan-3beta-yl acetate (3c) and 5alpha-bromo-6beta-methoxycholestan-3beta-yl acetate (4c). The benzoate 1d was not soluble enough in methanol, even with heating. The products were characterized by physical and spectral data (IR, 1H NMR and 13C NMR). Single crystal X-ray structure determinations of compounds 2a and 3a are also reported.

MATERIALS
Product Number
Brand
Product Description

Platinum, foil, not light tested, 25x25mm, thickness 0.002mm, as rolled, 99.95%
Platinum, foil, not light tested, 150x150mm, thickness 0.0075mm, as rolled, 99.95%
Platinum, foil, not light tested, 100x100mm, thickness 0.0075mm, as rolled, 99.95%
Platinum, foil, not light tested, 50x50mm, thickness 0.025mm, as rolled, 99.95%
Platinum, foil, not light tested, 50x50mm, thickness 0.025mm, as rolled, 99.99+%
Platinum, foil, not light tested, 50x50mm, thickness 0.002mm, as rolled, 99.95%
Platinum, foil, 25x25mm, thickness 0.1mm, as rolled, 99.95%
Platinum, foil, 25x25mm, thickness 0.1mm, as rolled, 99.99+%
Platinum, foil, 25x25mm, thickness 0.25mm, as rolled, 99.95%
Platinum, foil, 25x25mm, thickness 0.25mm, as rolled, 99.999%
Platinum, foil, 6mm disks, thickness 0.125mm, as rolled, 99.99+%
Platinum, foil, 0.5m coil, thickness 0.025mm, coil width 1.6mm, as rolled, 99.95%
Platinum, foil, not light tested, 50x50mm, thickness 0.0005mm, permanent polyester support, 99.85%
Platinum, foil, 10mm disks, thickness 0.005mm, as rolled, 99.95%
Platinum, foil, 10mm disks, thickness 0.01mm, as rolled, 99.95%
Platinum, foil, 15mm disks, thickness 0.05mm, as rolled, 99.95%
Platinum, foil, 1.2mm disks, thickness 0.025mm, as rolled, 99.95%
Platinum, foil, 15mm disks, thickness 0.004mm, as rolled, 99.95%
Platinum, foil, 15mm disks, thickness 0.0125mm, as rolled, 99.95%
Platinum, foil, 0.05m coil, thickness 0.025mm, coil width 1.6mm, as rolled, 99.95%
Platinum, foil, 0.2m coil, thickness 0.025mm, coil width .85mm, as rolled, 99.95%
Platinum, foil, 4mm disks, thickness 0.0125mm, as rolled, 99.95%
Platinum, foil, 15mm disks, thickness 0.1mm, as rolled, 99.99+%
Platinum, foil, 0.2m coil, thickness 0.030mm, coil width .7mm, as rolled, 99.95%
Platinum, foil, 25mm disks, thickness 0.0075mm, as rolled, 99.95%
Platinum, foil, 0.05m coil, thickness 0.2mm, coil width 5mm, as rolled, 99.95%
Platinum, foil, 0.2m coil, thickness 0.125mm, coil width 2.5mm, as rolled, 99.99%
Platinum, foil, 6mm disks, thickness 0.0075mm, as rolled, 99.95%
Platinum, foil, 15mm disks, thickness 0.125mm, as rolled, 99.95%
Platinum, foil, 0.5m coil, thickness 0.025mm, coil width 1.2mm, as rolled, 99.95%