Reaction of azinium cations. 5. Addition of water and methanol to 1,4-diazinium cations in the presence of bases. equilibrium constants and PMR spectra of the mono- and diadducts

Ring-Chain Transformations of Dihydroisoxazolo[4,5-b]quinoxaline

“…Studies on σ H adducts derived from azines and nucleophiles are often complicated due to reversibility of the corresponding processes, whereas cyclic adducts of 1,4-diazines with difunctional nucleophiles are more stable. There are published data on equilibrium addition of S-, O-, and N-nucleophiles to 1-alkylquinoxalinium salts [13][14][15]; furthermore, isolation of stable crystalline σ H adducts derived from 1-ethyl-2,3-dicyanopyrazinium ion has been reported in a few publications [16].…”

“…According to the 1 H and 13 C NMR data, compound III in CDCl 3 exists exclusively in the cyclic form. After dissolution of III in DMSO-d 6 , the intensity of signals belonging to the cyclic structure decreases, and those corresponding to covalent hydrate VI appear in the 1 H NMR spectrum of the solution.…”

“…Studies on σ H adducts derived from azines and nucleophiles are often complicated due to reversibility of the corresponding processes, whereas cyclic adducts of 1,4-diazines with difunctional nucleophiles are more stable. There are published data on equilibrium addition of S-, O-, and N-nucleophiles to 1-alkylquinoxalinium salts [13][14][15]; furthermore, isolation of stable crystalline σ H adducts derived from 1-ethyl-2,3-dicyanopyrazinium ion has been reported in a few publications [16].We previously reported on tandem reactions of 1,4-diazines and their quaternary salts containing an exocyclic carbonyl group with difunctional nucleophiles, resulting in fusion of five-, six-, and sevenmembered heterorings to the pyrazine ring. These cyclizations occur as intramolecular nucleophilic substitution of hydrogen and give rise to aromatic systems [7][8][9]12].…”

Transformations of C-adducts of 1,4-diazinium salts with dicarbonyl compounds into polycyclic systems

“…9- 13 As a rule, the presence of electron withdrawing groups in the starting azines imparts stability to σ H adducts, as can be judged from pK R+ , NMR spectroscopic data, electro chemical parameters, etc. 11 Actually, pyrazines contain ing alkoxycarbonyl, aminocarbonyl, or cyano groups in the ring can form stable mono and di σ H adducts. [12][13][14] The properties of these adducts remained unknown.…”