Molecular rearrangements yielding Δ2-pyrazolin-5-ones: acyloin rearrangement
Abstract
4-Hydroxy-3,4-diphenyl-Δ2-pyrazolin-5-one may be synthesized from 5-hydroxy-3,5-diphenyl-Δ2-pyrazolin-4-one by treatment with ethanolic sodium hydroxide or from 4-hydroxy-3,5-diphenylpyrazole by treatment with methanolic sodium carbonate in the presence of air; in both cases the reaction mechanism is thought to involve an acyloin rearrangement.