Dyes of a new class, incorporating the dihydro-1-oxoindolizine structural unit, have been synthesized. Oxo-indolizinium ions react with active methylene compounds to give dyes (Amm 560-630 nm) in high yield. The syntheses of the dihydro-1-oxoindolizinium ions and representative dyes from their reactions with active methylene compounds, along with the spectral and physical properties of the intermediates and the dyes, are presented. One ...
