Abstract A preparative route is proposed for the synthesis of the novel heterocyclic systems 7- oxo-and 1, 2, 7-trioxo-1, 2-dihydropyrano [3, 2-e] indole using classical Fischer and Sandmeyer methods respectively. We have studied various conditions for cyclization of the starting coumarin 6-isonitrosoacetamide and the methyl or ethyl pyruvate 6- coumarinylhydrazones. The syn-and anti-form ratio of the latter and the structure of all of ...