The role of geometry on regioselectivity and rate of fluorination of fluorene and diphenylmethane with Selectfluor™ F-TEDA-BF4
Abstract
Diphenylmethane and fluorene were used as target molecules in an investigation of the effect of the geometry of aromatic molecules on the regioselectivity and rate of fluorination with 1-chloromethyl-4-fluoro-1,4-diazoniabicyclo[2.2.2]octane bis(tetrafluoroborate)
(Selectfluor™ F-TEDA-BF4). In acetonitrile at 80 °C ring fluorination of diphenylmethane was accompanied by oxidation of the saturated carbon atom, while in trifluoroacetic acid only ring fluorination with an ortho–para regioselectivity of 1.8 ∶ 1 was observed. Fluorene was converted in acetonitrile as well as in trifluoroacetic acid into 2- and 4-fluoro substituted products in the relative ratio of 2 ∶ 1 and 1.2 ∶ 1, respectively. The reactions in acetonitrile obey a simple rate equation: