The Enantioselective Synthesis of (+)‐Estradiol from 1,3‐Dihydrobenzo[c]thiophene‐2,2‐dioxide by Successive Thermal SO₂‐Extrusion and Cycloaddition Reactions. Preliminary communication

The optically pure steroid (+)‐ 15 has been synthesized from the easily accessible (+)‐carboxylic acid 11 by a sequence of 7 steps in 50% overall yield. The key steps are the regioselective deprotonation/alkylation 7+13 → 14 and the thermal SO 2 ‐extrusion/cycloaddition 14 → 15 (Scheme 3) . The compound (+)‐ 15 has been readily converted to the naturally occurring (+)‐estradiol ( 17 ) in 60% yield.