Abstract
The new pyrrolocoumarin 3 was synthesized in two steps from 7-amino-4-methylcoumarin by selective o -chloroacetylation at position 8 and subsequent cyclization (the Sugasawa route to
indoles). Regioselective inverse electron demand Diels-Alder reaction of 3 with dimethyl 1,2,4,5-tetrazine-3,6-dicarboxylate or 3,6-bis(trifluoromethyl)-1,2,4,5-tetrazine
then gave the angular pyridazinepyrrolocoumarins 4 and 5 , respectively, in good yield.
Key words
antitumour agents - Diels-Alder reaction - electrophilic aromatic substitution - indoles
- polycycles
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