Propargyl bromide → Pregnane-3,20-dione

Participants

Reaction Conditions

Reaction Steps

A solution of 2-(2-propynyl)-2H-1,2,3-triazole (prepared by the reaction of triazole with propargyl bromide) (35 mg, 0.33 mmol) in dry THF (10 mL) was treated with n-BuLi (2.5M in THF, 0.33 mmol, 0.15 mL) at -70° C. After stirring the mixture at -75° C. for 0.5 hr, a solution of 5β-pregnan-3,20-dione, cyclic 20-(1,2-ethanediyl acetal) (60 mg, 0.16 mmol) in THF (10 mL) was added and the mixture was stirred at -78° C. for 1 hr. The cooling bath was removed and the mixture was quenched with NH4Cl solution (1 mL). The solvent was removed and the residue was then dissolved in acetone (25 mL). After adding 2N HCl (2 mL) the solution was stirred at rt for 30 min. Sat. NaHCO3 soln. was added to neutralize the acid. The solvents were removed and the residue was extracted with EtOAc. The organic layer was washed with water, and brine. After drying over anhyd. MgSO4 the solution was filtered and evaporated to yield the crude product. This crude product was then dissolved in a small amount of CH2Cl2 and poured on a column of silica gel. Elution with toluene:acetone mixture (85:15) gave pregnan-3,20-dione (20 mg) as a first fraction. Further elution with the same solvent yielded 3α-hydroxy-3β-[3-(2'H-1,2,3-triazol-2'-yl)-1-propynyl]-5β-pregnan-20-one (20 mg) as a colorless solid; mp 139-140° C.; TLC Rf (hexane:acetone 4:1)=0.17.

Provenance & Evidence