Direct electrophilic acylation of n-substituted pyrazoles by anhydrides of carboxylic acids

A simple, convenient and scalable approach to 1-substituted 4-acylpyrazoles through direct acylation of pyrazoles by anhydrides of aliphatic, aromatic and fluorinated carboxylic acids in the presence of concentrated sulfuric acid as a catalyst is described. Target ketones were obtained in 41-86% isolated yields in high purity without laborious purification. The scope and limitations of the method are discussed. © 2013 Georg Thieme Verlag Stuttgart New York.