The nature of ferrocenylalkylating agent in the acid-catalyzed reactions with ferrocenyl(phenyl)methanol

The reaction of α-ferrocenyl(phenyl)methanol with various azoles under the phase transfer catalysis conditions afforded a series of ferrocenyl(alkyl)azoles in high yields. The structure of ferrocenyl(phenylmethyl)-3-trifluoromethyl-5-(2-thienyl)pyrazole was established by X-ray diffraction. The formation of a biradical cation from the intermediately formed ferrocenyl(phenyl)-carbenium ion, FcCH(Ph)+, was detected by ESR spin trap technique. Despite the demonstrated possibility of the formation of biradical cations, no products characteristic of the radical reaction pathway were found, which may serve as an indirect evidence that the reaction follows the SN1-mechanism.