6a- Fluoroprogesterone

Addition to unsaturated steroids. The reagent adds slowly to testosterone acetate (a deactivated olefln) to give 4-fluorotestosterone. Pregnenolone acetate (1) affords an adduct (2) in modest yield, characterized by conversion into 6a-fluoroprogesterone, but the major product is a mixture of fluorinated by-products. 

Bromo [ F]fluoride (Section 3.9.1) addition across a double bond was used in the synthesis of fluorine-18-labelled steroids of high specific radioactivity. After addition, the bromine is removed by reduction or by dehydrobromination. [ F]Fluoro-5a-dihydrotestosterone was obtained in about 3% radiochemical yield (Scheme 17) [64] and 6a-p F]fluoroprogesterone in only 0.3% [65]. The yields were quite low but sufficient to allow for animal studies. These reactions had been tested out successfully with simpler model alkenes [66]. 

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