Switchable Site-Selectivite Direct Acetoxylation of Pyrazolones

Abstract

Site-selective direct acetoxylation of pyrazolones was accomplished by utilizing an easy-to-handle (diacetoxyiodo)benzene (PIDA) as the sole acetoxylating reagent. In the presence of Pd(OAc)2 catalyst, the 4-acetoxylated pyrazolone product was exclusively formed. Meanwhile, in the absence of Pd(OAc)2, the pyrazolone methyl acetate product was obtained over the Csp2−H bond functionalization. Both approaches have been successfully applied to various pyrazolone substrates, giving the corresponding products in moderate to high yields under mild conditions.