The 1,3-dihydroxy-5-oxonia-11-azabenzo[b]fluorene cation; a synthetic nitrogenous anthocyanidin

Abstract

The chalcone formed from salicylaldehyde and indoxyl cyclises in warm trifluoroacetic acid to yield the 5-oxonia-11-azabenzo[b]fluorene cation (Ib). The constitution of this has been confirmed by oxidation with hydrogen peroxide to the related flavone, [1]benzopyrano[3,2-b]indol-11-one (XI), also accessible by heating 2′-nitroflavone with ethyl phosphite.

The chalcone from indoxyl and 2,4,6-triacetoxybenzaldehyde is converted by trifluoroacetic acid into the 7,9-dihydroxy-5-oxonia-11-azabenzo[b]fluorene cation (Ia). Formally, this cation can be regarded as a nitrogenous anthocyanidin, and the possibility of its occurrence in plants is discussed briefly.