Bis (lactone) -annulated 4H-pyranes and 1,4-dihydropyridines from 3,3'- (nitrobenzlidene) -bistetronic acids
Görlitzer, K.; Trittmacher, J.; Bartke, U.
Die Pharmazie 57(9): 606-609
2002
ISSN/ISBN: 0031-7144 PMID: 12369446 Document Number: 544472
The bistetronic derivatives 4, obtained by base catalyzed reaction of the aldehydes 3 with surplus tetronic acid (2), cyclize in polyphosphoric acid (PPA) to yield the 4H-pyranes 5. The amino derivative 6 formed by reduction of the nitro group of 5a easily splits to give the furoquinoline 7 and 2. By heating the ammonium bistetronate 8 ring closure occurs leading to the bisannulated 1,4-dihydropyridine (DHP) 9. The DHP 9 is dehydrogenated to the corresponding pyridine 10. The half wave potentials of the 4H-pyranes 5 and 6 as well as the 1,4-DHP 9 are determined by differential pulse voltammetry.