A method for obtaining a new class of pyrimidinium ylides (type 3) is prese
nted. Their structures have been proved both by chemical and spectral metho
ds (including two-dimensional experiments: 2D-COSY, 2D-HETCOR and 2D-HETCOR
long range). The ability of the ylide to react with activated alkynes and
alkenes has been studied. The ylide (3) could act as an initiator in anioni
c polymerisation leading to oligomers.