
TY  - JOUR
A1  - Collins, DJ 
A1  - Hobbs, JJ 
T1  - Steroidal &#945;&#946;-Epoxyketones. II. Synthesis of 6&#945;-Bromo-4&#945;,5-epoxy-5&#945;-cholestan-3-one and Its 4&#946;,5&#946;-Isomer
JF  - Australian Journal of Chemistry
JO  - Aust. J. Chem.
Y1  - 1963
VL  - 16
IS  - 5
SP  - 874
EP  - 888
KW  - 
UR  - https://doi.org/10.1071/CH9630874 
N2  - An efficient method for the epimerization of 6&#946;-bromocholest-4-en-3-one (III) to 6&#945;-bromocholest-4-en-3-one (V) via 6-bromo-3-ethoxycholesta-3,5-diene (VI) is described.   Owing to the lability and unusual properties of several 6a-brominated intermediates, special experimental procedures were required for the conversion of (V) to 6&#945;-bromo-4&#945;,5-epoxy-5&#945;-cholestan-3-one (XVIII) and its 4&#946;,5&#946;-isomer (XVI). Thus, diborane reduction of 6&#945;-bromocholest-4-en-3-one (V) gave a high yield of the corresponding 3&#946;-alcohol (IV; R = H) which upon epoxidation with trifluoroperacetic acid and chromatography of the product over florid yielded 6&#945;-bromo-4&#946;,5-epoxy-5&#946;-cholestan-3&#946;-ol (XVII; R = H), and its 4&#945;,5&#945;-isomer (XV; R = H).   Chromic acid-acetone oxidation of the isomeric epoxyalcohols (XV; R = H) and (XVII; R = H) afforded 6&#945;-bromo-4&#945;,5-epoxy-5&#945;-cholestan-3-one (XVIII) and 6&#945;-bromo-4&#946;,5-epoxy-5&#946;-cholestan-3-one (XVI), respectively. 
ER  -

