ChemInform Abstract The rate constants of the two successive Diels-Alder additions of a given dienophile, e.g. methyl vinyl ketone, to the tetraenes (I) (synthesis described) or (V) are found to be nearly the same, thus making difficult the isolation of monoadducts in reasonable yields. Moreover, (I) and (V) and their corresponding adducts have a strong tendency to polymerize. Therefore, the synthetic potential of these compounds is very limited. In contrast, the diene (VI) is found to add strong dienophiles with good regio-and stereoselectivity. Reaction of (VI) with methyl vinyl ketone (IX) yields, depending on the quenching temp., the adduct (VII) or the ketone (VIII) (X-ray analysis: space group P21/n; Z=4). Compound (VII) is transformed to the triene (X) which adds to non-sym. dienophiles such as (XI) and (XIII) with good regioselectivity to give the polycycles (XII) and (XIV)/(XV), resp., which represent suitable anthracyclinone precursors.
The rate constants of the two successive Diels‐Alder additions of a given dienophile, e.g. methyl vinyl ketone, to the tetraenes (I) (synthesis described) or (V) are found to be nearly the same, thus making difficult the isolation of monoadducts in reasonable yields.
Starting with the bicyclooctenetetracarboxylates (II) and (VII), obtained by basic isomerization of (I), the bis‐ (XI) and tetramethylene derivatives (V) and (XII) are prepared.
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