title: [Bis(lactone)-annulated 4H-pyranes and 1,4-dihydropyridines from 3,3'-(nitrobenzlidene)-bistetronic acids].
abstract: 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.
mesh_terms: D004095:Dihydropyridines / Q000138:chemical synthesis* / Q000494:pharmacology; D004563:Electrochemistry; D005663:Furans / Q000138:chemical synthesis*; D007202:Indicators and Reagents; D007783:Lactones / Q000138:chemical synthesis*; D009682:Magnetic Resonance Spectroscopy; D011714:Pyrans / Q000138:chemical synthesis*; D013056:Spectrophotometry, Ultraviolet
chemical_list: D004095:Dihydropyridines; D005663:Furans; D007202:Indicators and Reagents; D007783:Lactones; D011714:Pyrans; C003422:tetronic acid
vernacular_title: Bislacton-anellierte 4H-Pyrane und 1,4-Dihydropyridine aus 3,3'-(Nitrobenzyliden)-bistetronsäuren.