Unusual behavior of 3,5-dimethylpyrazole in the aza-Michael reaction with crotonaldehyde in aqueous medium

Resumo

The aza-Michael reaction of 3,5-dimethylpyrazole with crotonaldehyde in water involved addition of two aldehyde molecules with formation of 2-[2-(3,5-dimethyl-1H-pyrazol-1-yl)propyl]-6-methyl-1,3-dioxan-4-ol. The latter exists in solution as equilibrium mixture with monocyclic 3-{[3-(3,5-dimethyl-1H-pyrazol-1-yl)-1-hydroxybutyl]oxy}butanal.