Synthesis of Steroidal Thioethers via [HDBU][OAc]‐Mediated Michael Addition of Thiols to 16‐Dehydropregnenolone

In the catalytic addition of thiols to 16-dehydropregnenolone fourteen thioethers were prepared via thiol-Michael addition reaction in the presence of different aliphatic and aromatic thiols as reagents. [HDBU][OAc] was proved to be an efficient catalyst and solvent providing thioether derivatives in good to excellent yields. The ionic liquid could be reused for five times without noticeable loss of activity. The structures of compounds were confirmed by H-1-, C-13 NMR and IR spectroscopy and mass spectral analysis. A series of these pregnenolone derivatives were evaluated for their cytotoxic activity on breast cancer (MDA-MB-231, MCF7) cell lines.