A comparative study of remote oxy-functionalization of unactivated carbons in 5β-steroids by dimethyldioxirane and 2,6-dichloropyridine N-oxide / ruthenium-porphyrin / HBr

2003 ARKIVOC  
Remote oxy-functionalization of methyl 3α-acetoxy-and 3-oxo-5β-cholan-24-oates with 2,6dichloropyridine (DCP) N-oxide catalyzed by (5,10,15,20-tetramesitylporphyrinate) ruthenium (II) carbonyl complex [Ru(TMP)CO] and HBr was compared with that with dimethyldioxirane (DMDO). Treatment of the 5β-steroids with DMDO afforded the corresponding 5β-and 17αmonohydroxylated and 5β,14α-and 5β,17α-dihydroxylated compounds. On the other hand, the corresponding 20S-mono-and 5β,20S-dioxygenated derivatives
more » ... s the γ-lactones), along with 5β-hydroxy compounds, were found to be the major oxidation products of the 5β-steroids with the DCP N-oxide / Ru(TMP)CO / HBr system. Both the reagents oxidized unactivated methine carbons stereoselectively, but the degree of regioselectivity depended upon the oxidants employed and the structure of the hydroxyl-protecting groups at C-3 (acetoxyl or carbonyl) of the substrates.
doi:10.3998/ark.5550190.0004.817 fatcat:4vsfhmbcavbefkof5ulz5t7rua