5alpha-Dihydroprogesterone → Ganaxolone

Participants

Reaction Conditions

Reaction Steps

A mixture of ferric chloride (anhydrous, 1.63 g, 10.06 mmol) in tetrahydrofuran (anhydrous, 35 ml) is cooled to −50° C. under nitrogen. Methyllithium (3M, 3.4 mL, 10.2 mmol) in diethoxymethane is added to the ferric chloride mixture, maintaining the temperature below −40° C. After this addition is complete methyl magnesium chloride solution (3M, 10.1 ml, 30.18 mmol) in tetrahydrofuran is added maintaining the internal temperature below −40° C. After 10 min. at −40° C., 5α-pregnane-3,20-dione (2.84 g, 9 mmol) is added in one portion with stirring. The temperature is brought to −20° C. and stirred for 3.5 hours. The reaction is quenched by addition of 3 ml of acetic acid and the tetrahydrofuran was removed in vacuo. The residue is partitioned between 100 ml of 3N HCl and 200 ml of ethyl acetate. The organic layer is washed with 1N sodium hydroxide and brine and the solvent is removed in vacuo to afford crude ganaxolone (94.8% purity by HPLC) (Table 1, entry 5)

Provenance & Evidence