ortho-Allylation of 1-Arylpyrazoles via Iron-Catalyzed C-H Bond Activation

Nakamura et al. have reported an ortho-allylation of 1-arylpyrazoles with allyl phenyl ethers via iron-catalyzed C-H bond activation. In the presence of Fe(acac)₃ / 4,4'-di-tert-butyl-2,2'-bipyridyl (abbrev.: dtbpy) and in situ prepared diphenyl zinc, the reaction proceeds at 0 ºC to afford the ortho-allylated product. In this reaction, no allylated products are obtained without using the iron catalyst and also, no deuterated products are obtained after treatment with D₂O instead of allyl phenyl ethers. On the other hand, in the presence of the iron catalyst, a deuteration at the ortho-position of 1-arylpyrazoles is performed by the treatment with D₂O. These results suggest that this allylation proceeds via the possible formation of an iron-intermediate generated by iron-catalyzed C-H bond activation.