Combination of Pyridinium and Isoquinolinium Ylides with Phenylisocyanate and Isothiocyanates: Synthesis, Characterisation, and X-Ray Crystal Structures of Mesoionic Monosubstituted 3-Oxo-Propanamides or Thioamides

Abstract

Pyridinium ylides derived from 2-bromoacetophenone or methyl bromoacetate have been reacted with phenylisocyanate, phenyl- or methylisothiocyanate to afford mesoionic monosubstituted 3-oxo-propanamides or thioamides, via self-protonation of the intermediate N-anion. A similar reaction under the same conditions of isoquinolinium ylides with phenylisocyanate or phenyisothiocyante also produced the corresponding mesoionic compounds. In order to establish the exact structure of the mesoionic compounds, single crystal X-ray structures were obtained for three of the pyridinium ylides.