Elie Stephan

BORON TRIFLUORIDE PROMOTED ADDITION OF ARYLLITHIUMS TO ESTRONE BENZYL ETHER

Abstract aryllithiums did not condense with estrone benzyl ether at low temperature. The promoted addition with boron trifluoride etherate was the best method for preparing substituted 17α-arylestradiols.

Improved synthesis of a protected 11-oxoestrone

An improved synthesis of 11-oxoestrone-3-acetate-17-ethyleneketal is reported. Adjustments are proposed for the oxidation of estrone by 2,3-dichloro-5,6-dicyano-1,4-benzoquinone into 9(11)-dehydroestrone. A complete hydroboration-oxidation of the resulting ketal, by means of borane-methylsulfide complex, gives the corresponding 11-hydroxy derivative. This latter compound is then acetylated for successful oxidation with pyridinium chlorochromate on alumina. The overall yield is 30%.

Soft cleavage of THP protected estradiols mediated by TMSI

Treatment of 3-tetrahydropyranyloxy-17α-aryl estradiols, dissolved in acetonitrile or acetonitrile/THF/pentane mixture, with trimethylsilyl iodide resulted in the soft deprotection of THP ether in good yields without side dehydratation.

Access to new steroids via a (1,2) Wittig rearrangementt

Novel steroids are obtained by reaction of 9,11-dehydro-dibenzylestradiol and dibenzylestradiol with phenyllithium in THF at room temperature.