Access toward steroid skeleton and its derivatives via copper‐catalyzed intramolecular cyclization: A short synthesis of estradiol and estrone.

A practical and efficient approach leading to [6,6,6,5] tetracyclic fused ring steroid skeletons (8 a–i) has been designed through copper catalyzed intramolecular [4+2] cycloaddition reaction of enyne‐carbonyl substrates (7 a–i). The compound 8 a having OMe group at aromatic ring was further utilized to synthesize estradiol and Estrone. [ABSTRACT FROM AUTHOR]