4-Methylpyrimidinium ylides, 1

For the first time in the pyrimidinium ylides series we present a theoretic al and experimental study concerning the structure, stability and reactivit y of pyrimidinium ylides and interesting correlations between these propert ies. Methylpyrimidinium ylides are relatively stable compounds, their stabi lity varying with the nature of the ylide carbanion substituent. The more e lectron-withdrawing these substituents, the more the anionic charge is delo calized and therefore the higher the stability. The data from experiments a nd quantum chemical calculations are in agreement with each other. The quan tum chemical calculations show the possibility of using pyrimidinium ylides as nucleophilic reagents as well as 1,3-dipoles in reaction with appropria te reagents.:Eight new pyrimidine compounds (4 salts and 4 ylides) were obt ained.