Anilinopyrylium salts. Their synthesis and conversion to other heterocyclic systems

Abstract

Two methods for the preparation of anilinopyrylium salts are described. The conversion of these salts to pyrans, pyridines, and nitrobenzenes is discussed. Azepines, benzimidazoles, and benxotriazoles are readily obtained from the o‐aminoanilinopyrylium salts.

E/Z Conformational equilibrium of N-substituted 2H-pyran-2-imines

“…Compounds 4 were found to exhibit at the NMR time scale E, Z-conformational equilibrium at the exocyclic C, N bond. Surprisingly, no experimental evidence for such equilibrium was provided by earlier reports on N-4,6-triphenylpyran 2-imine (4, R = R' = Ph) [2][3][4][5] or other pyran 2-imines 6,7 and benzoannelated analogs [8][9][10][11][12][13] . By contrast, the hindered rotation around C,N double bond in Naryl-2,6-dimethyl-4H-pyran-4-imines 5 and related iminium salts 6, 7 (Scheme 2) had been extensively investigated by 1 H, 13 C and 15 N NMR in the early eighties.…”

1,3,5-Triaryl-2-penten-1,5-dione anchored to insoluble supports as heterogeneous chromogenic chemosensor

“…synthetized as described in the literature,14,15 was added. The mixture was stirred at reflux temperature for 3 h, then cooled at room temperature and stirred for 20 h. The solvent was removed under reduced pressure and the resulting brownish, red oil used for the next step without purification.4.1.3.…”

The influence of exocyclic lone pairs on the bonding and geometry of type A mesoionic rings

“…To explore whether similar anomeric effects are found in other heterocyclic rings with exocyclic substituents, we have calculated properties of the pyrone derivatives 17a-d. N,4,6-Triphenypyran-2-imines are known [23,24], and Uncuţa and coworkers, in a detailed NMR study, have shown that in equilibrium mixtures, e.g., 17b,c, the trans (Z) configuration prevails [25].…”