Kranjc K, Polanc S, Kocevar M. Diels-Alder reactions of fused pyran-2-ones with maleimides: efficient syntheses of benz[e]isoindoles and related systems.
Org Lett 2003;
5:2833-6. [PMID:
12889886 DOI:
10.1021/ol034852q]
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Abstract
[reaction: see text] The Diels-Alder reaction of some substituted 5,6,7,8-tetrahydro-2H-1-benzopyran-2-ones (1a-f) with N-substituted maleimides (2a-c) leading to fused isoindole derivatives (5a-n, 7) or, in a few cases, to bridged double cycloadducts (fused bicyclo[2.2.2]octene derivatives) (6a-f) is presented. When X = CO, the first efficient, substituent-driven aromatization of an intermediary-formed cycloadduct was observed, resulting in substituted benz[e]isoindoles (5a-k). The same type of aromatization can also be achieved in an unprecedented catalysis with Rh/C.
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