Regioselective Diels–Alder addition to 2-benzopyran-3-ones; a route to aromatic steroids
Abstract
2-Benzopyran-3-one (1; X = H) undergoes strongly regioselective Diels–Alder additions to buta-1,3-diene, isobutene, but-1-ene, and the olefin (6); the adducts derived from (6) and either (1; X = H) or (1; X = OMe) are readily transformed into the aromatic steroids: (9), (10), (17), (18), 9-epi-(10), 9-epi-(18), the naphthalene (14), and the dihydronaphthalene (15).