A very short synthesis of steroids from 1,3-butadiene and benzocyclobutenes

Lewis acid mediated addition of 1,8-bis(trimethylsilyl)octa-2,6-diene (BISTRO) 1 to succinic anhydride led to spirolactone 2 [(+/-)-6,9-divinyl-1-oxaspiro[4.4]nonan-2-one]. Methoxycarbonylation followed by stereoselective alkylation by various benzocyclobutenes afforded the substituted benzocyclobutene steroid precursors 5. Thermolysis of 5 gave rise to steroids (+/-)-6 with a trans-anti-cis configuration in five steps and in a highly stereoselective manner. Modifications of the sequence allowed the preparation of steroids (+/-)-11 with trans-anti-trans configuration.