ChemInform Abstract: Photooxygenation of Styrenic Estrogens: Structural Analysis of 8,9‐ Didehydro‐, 6,7‐Didehydro‐, and 9,11‐Didehydroestrone Derivatives and Their Reactivity Toward Singlet Oxygen.

Abstract

Photooxygenation of Styrenic Estrogens: Structural Analysis of 8,9-Didehydro-, 6,7-Didehydro-, and 9,11-Didehydroestrone Derivatives and Their Reactivity Toward Singlet Oxygen.-The three title compounds (I), (III), and (VIII) with the ring-A-conjugated double bond at three different possible positions, and the dinoranalogue (X) are submitted to photooxygenation according to method A). As already stated (I) affords only the product (II) of cleavage of the 9,11-double bond possibly via a 1,2-dioxetane intermediate. Compound (III) yields (IV), probably via (2 + 2) cycloaddition and subsequent cleavage, (V), the primary ene-type reaction product, and the products (VI) and (VII). The latter are conversion products of primarily formed (ene-type reactions) allylic hydroperoxides. The compounds (VIII) and (X) yield the products (VII) and (XII) derived from primary ene-type products such as (IX). Kinetic studies on (I) and (III) and conformational X-ray analyses of the substrates (I), (III), (VIII), and (X) are carried out. The aim of these investigations was to test the reactivities of rings B and C toward singlet oxygen. The results may give rise to novel syntheses within this class of compounds. -(MALET, C.; PLANAS, A.; BROSA, C.; PINIELLA, J. F.; RIUS, J.; Helv.