Synthesis and oxidation of all isomeric 2-(pyrazolyl)ethanols

An efficient approach to the preparation of N-substituted 2-(pyrazol-4-yl)ethanols based on recyclization reaction of 3-(dimethoxymethyl)-2-methoxytetrahydrofuran with hydrazines is described. Oxidation by KMnO₄ led to 2-(pyrazol-4-yl)-2-oxoacetic acids. In contrast, 2-(pyrazol-5-yl)ethanol under similar conditions gave only pyrazole-5-carboxylic acid, which formed as a result of oxidation followed by decarbonylation. 2-(Pyrazol-3-yl)ethanol in this oxidation reaction gave a mixture of 2-oxo-2-(pyrazol-3-yl)acetic acid and pyrazole-3-carboxylic acid.