Applications of high-potential quinones. Part 13. Dehydrogenation of de-A-estra-5,7,9-trienes to styrenes

Abstract

The de-A-estratrienes (1)–(6) yield the corresponding de-A-estra-5,7,9,14-tetraenes (8)–(13) by oxidation with an equimolar amount of dichlorodicyanobenzoquinone in dioxan at room temperature. The rates of dehydrogenation ate sensitive to changes in substituents at C-17. Similar rate ratios are observed for the alcohol–acetate pairs (1)–(2) and (3)–(5), indicating a mechanism involving direct attack at the benzylic position in both the phenols and their methyl ethers. Deoxygenation of the phenol (3) was carried out by cleavage of the diethyl phosphate ester with lithium in liquid ammonia, but could not be achieved by cleavage of the phenyltetrazolyl ether