Unusual electrochemical oxidation of cholesterol

A selective electrochemical method of glycosylation of 3β-hydroxy-Δ5-steroids

“…Cholesterol (from Aldrich, 99+%) and a sugar substrate were introduced into the anodic compartment whereas anionite (2.5 g, Dowex 2x8, 200-400 mesh, perchlorate form) was placed in the cathodic compartment to eliminate chloride ions formed by the reduction of dichloromethane. 12 The solutions in both compartments were stirred during electrolysis and additionally a continuous flow of argon was applied in the anodic compartment. Platinum mesh was used as a cathode and platinum plate (3 Â 1.5 cm) or glassy carbon plate (2.7 Â 1.5 cm) was used as anodes.…”

“…The detailed analysis of the reaction mixture led to isolation and identification of the minor reaction products -3, 4, 5, and 6. Dicholesteryl ether 3 has been isolated in the previous study 12 as the major product in the absence of a sugar in the reaction mixture. Cholesteryl acetate 4 has also been isolated previously as a result of reaction of the carbocation with acetate leaking from the electrolytic bridge.…”

“…Formation of a non-classical homoallylic carbocation during cholesterol electrooxidation was convincingly proved. 12 Such carbocations may react with any nucleophile present in the reaction mixture providing various products of substitution at C-3 with retention of configuration.…”

“…Our recent study on direct electrooxidation of cholesterol in dichloromethane, which stabilizes cationradicals and is devoid of nucleophilic properties, led to quite different results. 12 Surprisingly, the reaction occurred exclusively at the hydroxyl group at C-3. The initially formed cation-radical underwent cleavage to homoallylic carbocation and hydroxyl radical ( Fig.…”

Investigation of the Appel reaction with bromotrichloromethane-triphenylphosphine (CBrCl3/PPh3)

“…Cholesteryl chloride (3β-chlorocholest-5-ene, 12-Cl) [12] Earlier we had already reported that in our hands the reaction of 2-phenylethanol (1) with PPh3-BrCCl3 in CH2Cl2 at rt led to a mixture of 2-phenylethyl bromide (2-Br) and 2-phenylethyl chloride (2-Cl) in a 6:4 ratio (Scheme 1) [14]. Thereafter, the authors investigated whether this trend holds true with other substrates ( Table 1.…”