Synthesis and spectral properties of vinylogs of heterylpolyenes based on pyran
Vinylogs of unsymmetrical benzothiazole- and indolenine-substituted polyenes — pyran derivatives — were synthesized. Their absorption spectra reveal that the vinylene shift decreases with an increase in the length of the chromophore. The deviations of unsymmetrical heterylpolyenes prove to be negative and, for the same length of the chromophore, increase in absolute value with an increase in the difference in the electron-donor character of the terminal groups.