Dioxopyrroline dienophiles

On the other hand, as already mentioned in the introduction to this section, the Diels-Alder addition of 1,3-butadienes to dioxopyrroloben-zazepine, e.g. according to reaction 136 - - 137b —> 138b (Scheme 19) gives only very poor yields (<5%). This has been attributed to the marked conformational difference between the two dioxopyrroline dienophiles 137a and 137b (77). 

More recently, dioxopyrrolines have been introduced as classical , electron-deficient dienophiles. For example, the addition of (in situ prepared) 3-aryldioxopyrroline (43) to butadiene afforded the hexahy-droindole (44), a key precursor in a synthesis of Amaiyllidaceae alkaloids (Scheme IS). Similarly, highly regioselective [4 -i- 2] cycloaddition of isoquinolinodioxopyrroline (46) to l,3-bis(tiimethylsily-loxy)butadiene (45) afforded the tetracyclic adduct (47) with excellent control over the relative configuration of two quaternary and one tertiary stereogenic centers. Cycloadduct (47) served as a pivotal intermediate in erythrina alkaloid synthesis. ... 

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See also in sourсe #XX -- [ ]

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