Electrophilic Fluorination with Elemental Fluorine and Reagents Derived from it
Pp. 3-41 (39)
Elemental fluorine is a highly reactive reagent which could destroy
almost any organic compound or perfluorinate it under controlled conditions.
However, under the right set of conditions, it may act as an electrophile and as
such, it can be a powerful electrophile indeed. This chapter describes some
regio- and stereospecific electrophilic fluorination at saturated tertiary sp3
centers, which are usually very unreactive and cannot participate in specific
organic reactions. It was concluded that the higher the hybridization on p of
these centers, the better is the outcome of the reaction. In many cases, the
substitution of such tertiary hydrogen takes place in yields of 70% and more.
Such fluorinations, which were carried out on a wide variety of organic
compounds, provide an excellent opportunity for dehydrofluorination
reactions to form double bonds and hence are considered to enable
functionalization of “impossible sites” in organic molecules. Elemental
fluorine was also used for fluorination of double bonds, in a syn mode,
replacing the old and inefficient method of reacting olefins with Pb(OAc)4 and
HF. Acetyl hypofluorite is easily and readily made from sodium acetate and F2.
It proved to be a very useful reagent for fluorination of activated aromatic
compounds, for addition across double bonds, in order to synthesize
biologically important fluorine containing derivatives, for constructing α-
fluoro carbonyl and ether derivatives and for use in Positron Emitting
School of Chemistry, Tel-Aviv University, Tel-Aviv 69978, Israel.