| abstract |
Described is a process for the regioselective dehydration of 11-hydroxy steroids using PCl5, PCl3, POCl3 or either SO2Cl2 and imidazole, or PPh3 and CCl4. The disclosed process selectively forms DELTA <9,11> steroids from either 11- alpha - or 11- beta -hydroxy steroids, and can also be used for the one-step conversion of 11,21-dihydroxy steroids to 21-chloro- DELTA <9,11> steroids. Also disclosed are processes for the regioselective conversion of 11- beta -chloro steroids to DELTA <9,11> steroids, and for regioselectively converting an 11,17,21-trihydroxy steroid to a 21-chloro-11,17-dihydroxy steroid. |