CYCLIZATION OF SUBSTITUTED (2-PYRIDYLTHIO)PHENYLACETIC ACIDS AND CHROMATICITY OF MESOIONIC THIAZOLO[3,2-a]PYRIDINIUM-3-OLATES

摘要

The cyclization of substituted (2-pyridylthio)phenylacetic acids has been studied. It was established that reaction occurs at two reaction centers with the formation of substituted 3-imino-2-phenyl-2,3-dihydrothieno[ 2,3-b]pyridine-2-carboxylic acids and substituted mesoionic thiazolo[3,2-a]pyridinium-3-olates. The direction of cyclization is influenced by the acidity of the medium and the character of the substituents in the pyridine nucleus. The spectral properties of the synthesized mesoionic compounds were investigated experimentally and theoretically (by the Pariser–Parr–Pople method).