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|Title:||Smooth generation of 3H-2-benzopyron-3-ones and their Diels-Alder reactions with olefinic dienophiles||Authors:||van Broek, P.I.
Kieckens, Eric G.
|Issue Date:||1991||Source:||Journal of the Chemical Society: Perkin transactions I. p. 639-644||Abstract:||The generation of methoxy-substituted 3H-2-benzopyran-3-ones from o-acylphenylacetic acid derivatives in acetic anhydride at 140 °C and their in situ Diets–Alder reactions being inefficient in the synthesis of some carbocyclic compounds, alternative reagents have been used. It is shown that, e.g. 1,3-dicyclohexylcarbodiimide (DCC) with 2-hydroxypyridine, disuccinimidyl carbonate (DSC), 2-ethoxy-N-ethoxycarbonyl-1,2-dihydroquinoline (EEDQ) of 2-isobutoxy-N-isobutoxycarbonyl-1,2-dihydroquinoline (IIDQ) are much more efficient reagents.Using these alternative reagents the formation of side-products from the benzopyranone, e.g. chrysene, can be avoided; with the modified DCC-method the 6,7-dimethoxy-1 -methyl-2-benzopyran3-one intermediate 8a can be identified spectroscopically. An exemplified procedure with IIDQ is proposed, opening new prespectives for Diets–Alder reactions of unstable or less reactive dienophiles with problematic benzopyranones.||Document URI:||http://hdl.handle.net/1942/4394||DOI:||10.1039/P19910000639||Type:||Journal Contribution|
|Appears in Collections:||Research publications|
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