If the conversion of 6β hydroxy 6α,17α dimethylpregn 4 ene 3,20 dione into Medrogestone is carded out with {HEAD ~ the Lewis acid}, boron trifluoride etherate, rather than with the more conventional agents such as SOCl2 /pyridine, POCl3 /pyridine or MsCl/Et3 N/DMAP/CH2 Cl2, reaction temperatures below {TAIL ~ about 65° C.} are feasible and isomerization to 6,17α dimethylpregna 6,8 diene 3,20 dione is largely avoided 
If the conversion of 6β hydroxy 6α,17α dimethylpregn 4 ene 3,20 dione into Medrogestone is carded out with { HEAD ~ the Lewis acid } , boron trifluoride etherate , rather than with the more conventional agents such as SOCl2 /pyridine , POCl3 /pyridine or MsCl / Et3 N / DMAP / CH2 Cl2 , reaction temperatures below { TAIL ~ about 65 ° C. } are feasible and isomerization to 6,17α dimethylpregna 6,8 diene 3,20 dione is largely avoided
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