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Paper | Regular issue | Vol 89, No. 11, 2014, pp.2572-2587
Published online, 5th November, 2014
DOI: 10.3987/COM-14-13094
A Diversity-Oriented Approach to 1H-Pyrazole-4,5-diols, 4-Hydroxy-3H-pyrazol-3-ones, and Phenylhydrazones from Key Intermediate 4-Acetyloxy-3H-pyrazol-3-one

Eiichi Masumoto, Fumi Okabe, Toshihiro Fujioka, Kenji Yamagata, and Hiroshi Maruoka*

*Faculty of Pharmaceutical Sciences, Fukuoka University, 8-19-1 Nanakuma, Jonan-ku, Fukuoka 814-0180, Japan


An approach to 1H-pyrazole-4,5-diols 4ad, 4-hydroxy-3H-pyrazol-3-ones 5ad, and phenylhydrazones 6ad from key intermediate 4-acetyloxy-3H-pyrazol-3-one 3a is described. 4-Alkylidene-3H-pyrazol-3-ones 1ac were reacted with m-chloroperbenzoic acid in the presence of potassium carbonate to give the corresponding spiroepoxide-3H-pyrazol-3-ones 2ac. Treatment of 2a with acid anhydride such as acetic, propionic, butyric, and pentanoic anhydride in the presence of boron trifluoride diethyl etherate led to the corresponding 4-acyloxy-3H-pyrazol-3-ones 3ad. The reactions of 3a with α-chloroketones, ketones, and/or secondary amines gave the corresponding 4ad, 5ad, and 6ad.