6-Oxoestradiols from estradiols: Exploiting site selective metalation of aralkyl systems with superbases

Article abstract of DOI:10.1055/s-1995-4136

3-O-Protected estradiol derivatives undergo metalation at C-6 when exposed to a fourfold excess of the reagent consisting of an equimolar mixture of lithium diisopropylamide and potassium 1,1-dimethylpropoxide (3 h, THF, -78°C). The metalated intermediates can be oxidized by quenching with trimethyl borate followed by treatment with hydrogen peroxide, thus allowing the introduction of a 6-hydroxy group into the estradiol framework. Further oxidation of the 6-hydroxy group gives O-protected 6-oxoestradiols.