α,α'-Dioxothiones part 2. Asymmetric Diels-Alder reactions of chiral non-racemic α,α'-dioxothiones

Article abstract of DOI:10.1016/S0040-4020(97)10162-4

Chiral non-raemic α,α'-dioxothiones 2a-g and 17 are obtained from chiral β-ketoesters using the phthalimidesulfenyl chloride 1 as key reagent. The ability of these thiones to discriminate between the enantiotopic faces of several dienophiles has been evaluated. The best diastereoisomeric excesses (67-80%) were obtained when the a-acyl thiones were involved as electron-poor dienes in inverse electron demand Diels-Alder reactions with electron-rich styrenes as dienophiles. The possibility to obtain thiones bearing two chiral groups as well as the reactions where the a-acyl thiones 2 participate as dienophiles are also shown.