Vilsmeier-Haak Formylation of 3,5-Dimethylpyrazoles

摘要

Formylation of N-alkyl-3,5-dimethyl-lH-pyrazoles according to Vilsmeier-Haak led to the formation of the corresponding 4-formyl derivatives.3,5-Dimethyl-lH-pyrazole having no substituent on the nitrogen atom failed to undergo formylation at the 4 position under analogous conditions.3,5-Dimethyl-1H- pyrazole-4-carbaldehyde was synthesized by alkaline hydrolysis of methyl p-(4-formyl-3,5-dimethyl-lH-pyra- zol-l-yl)propionate and subsequent heating of the acid thus formed.