Synthesis of dienic ?-dimethylamino-?-methyl(phenyl)carbonyl compounds and a study of their valence isomerism employing ultraviolet and infrared spectroscopy

Abstract

1. Some previously unknown dienic δ-dimethylaminocarbonyl compounds, containing a substituent (Me or Ph) in the γ position, were synthesized. The δ-aminodienone-2-amino-2H-pyran valence isomerization was discovered and studied (via the UV and IR spectra) for the first time on the example of these compounds. 2. The existence of a dynamic equilibrium between both valence isomers was established. The equilibrium is shifted toward the δ-aminodienones with increase in the temperature, and also the dielectric constant of the solvent and its capacity for specific solvation. An especially strong change occurs when the amount of water in organic solvents is increased. 3. The dienic δ-amino-γ-methyl(phenyl)carbonyl compounds exhibit a clearly expressed solvatochromism, the nature of which depends on the valence isomerization. 4. The aggregate state can exert an effect on the existence of the δ-aminodienones as either valence isomer; 6-dimethylamino-3-carbomethoxy-5-methyl-3,5-hexadien-2-one in the crystalline state represents the dienone, while in the molten state it represents the 2Hpyran.