Formylation of 2-Methylpyrimidine-4,6-diol Under the Conditions of the Vilsmeier–Haack Reaction

In the course of this work, we explored the influence of the conditions of the Vilsmeier–Haack reaction for 2-methylpyrimidine-4,6-diol (<b>1</b>). We conducted a comparative analysis of approaches using various solvents (o-xylene, N,N-dimethylformamide (DMF), benzene, and dichloroethane) as the reaction medium, and the optimal one was selected. During the formylation of substrate 1 in these conditions, only 4,6-dihydroxy-2-methylpyrimidine-5-carbaldehyde (<b>2</b>) was successful. It should be noted that there was no substitution of hydroxyl groups for chlorine atoms observed in reactions with similar substrates. The structure of the resulting product <b>2</b> was proven using NMR spectroscopy on ¹H and ¹³C nuclei and by mass spectrometry.