Synthesis and optical properties of 5-substituted 2-(2-tosylaminophenyl)benzoxazoles

Various 5-substituted 2-(2-tosylaminophenyl)benzoxazoles were synthesized. The presence of intramolecular hydrogen bonding, the strength of which depends on the nature of the substituent, was shown by means of the IR spectra of the investigated series of compounds. A correlation between v_NH and the Taft substituent constants was found. The investigated benzoxazoles have fluorescence in the yellow-green region of the spectrum; an anomalously large Stokes shift is characteristic for them. The position of the fluorescence spectrum depends on the strength of the hydrogen bond: when it becomes weaker, the spectrum is shifted bathochromically.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 472–478, April, 1973.