Synthesis of 5,7‐Dihydrodibenzo[b,f][1,7]naphthyridine‐6,12‐dione, an Unexpected Isolate from Isatis tintoria

Abstract

The dye plant Isatis tinctoria yields a number of heterocyclic compounds with interesting antiinflammatory and cytotoxic properties, formed mainly in an unknown manner by post-harvest treatment. A synthesis of the incidently isolated 5,7-dihydrodibenzo[b,f][1,7]naphthyridine-6,12-dione (4a) is presented. Starting from different 1,2-diarylhydrazines, adducts 11 with acetylenedicarboxylates (¼ but-2-ynedioates) are thermally treated (Scheme). In a Fischer-type rearrangement, 3-(arylamino)quinolinecarboxylic acids 9 are obtained, which can be cyclized under Friedel -Crafts conditions to yield a number of analoga 4 of the title compound.

Rearrangement of 7-Aryloxazolo[5,4-b]pyridines to Benzo[c][1,7]naphthyridine-4(3H)-ones and Thieno[3,2-c][1,7]naphthyridine-6(7H)-ones

“…The known representatives of the fused derivatives of this heterocyclic system are benzo­[ f ]-, benzo­[ b ]-, , dibenzo­[ b , f ]-, and dibenzo­[ c , f ]­[1,7]­naphthyridine-6­(5 H )-ones, as well as pyrrolo­[2,3- c ]­[1,7]­naphthyridine-6-ones . Benzo­[ c ]­[1,7]­naphthyridine-4­(3 H )-ones and thieno­[3,2- c ]­[1,7]­naphthyridine-6­(7 H )-ones remained unknown for a long time.…”

Cyclization Reactions of 3,4-Diazaheptatrienyl Metal Compounds. Pyridines from an Anionic Analogue of the Fischer Indole Synthesis: Experiment and Theory

“…Pyridines are among the most important and versatile organic substances that are known to organic chemistry. They are widely used as pharmaceuticals and agrochemicals, as ligands, and in organocatalysis. , Thus, the development of new synthetic routes for pyridines has always been in the focus of organic chemists. − Hydrazones, on the other hand, are reactive starting compounds for organic synthesis with the Fischer indole rearrangement as the best known example . In our group, we have learned that cationic and anionic intermediates derived from unsaturated hydrazones are interesting precursors for unprecedented ring-closure reactions preceding under mild conditions. , N–N bond fission, sometimes observed in such compounds, is an additional synthetically useful property .…”

“…However, as this study will show below, this particular work combines the ring-forming aptitude of azapolyenyl anions 1 with a novel, unexpected organometallic rearrangement reminiscent of the mechanism of the Fischer indole synthesis . It outlines a procedure that allows the synthesis of pyridines or more complex analogues from commercially or easy available substrates.…”

4-Quinolone fused heterocyclic ring systems by intramolecular reactions of 4-quinolone-2-carboxamides

“…Riepl et al reported the preparation of 5,f] [1,7]naphthyridine-6,12-diones by a Fischer type rearrangement reaction. 15 However, the versatility of this methodology was strongly limited by the need to use freshly prepared symmetric 1,2-diarylhydrazines. To evaluate the influence of the chain length on the cyclization, the reactivity of δand ε-oxamides was investigated as well.…”

“…4.7.3. 1,10 .0 4,9 .0 15,20 ]icosa -4,6,8,12,15(20),16,18-heptaene-11,14-dione (15). Compound 14 (265 mg, 0.86 mmol) was heated at refluxrefluxed for 7 h with IBX to give 4-oxo-1,4-dihydroquinoline-2-carboxylic acid 2-(2-oxoethyl)benzylamide; white solid; Rf :…”