[13873-84-2] · FI · Iodine Monofluoride · (MW 145.90)
Preparative Methods: unlike most organic reagents, the notation of [IF] has been used to designate a two-step reaction taking place when a mixture of two different agents, one a source of electrophilic iodine and the other of nucleophilic fluorine, is reacted with a substrate. The true molecule of IF can be prepared in situ by a reaction between the corresponding elements5 or by reacting Iodine with IF56 or iodine with Silver(I) Fluoride.7 Many reactions, but not all, of [IF] and IF are quite similar.
Handling, Storage, and Precautions: use in a fume hood.
Adding the elements of iodine and fluorine across double bonds by using N-Iodosuccinimide (NIS) and anhydrous Hydrogen Fluoride is an old procedure employed extensively in steroid chemistry (eq 1).10 The addition proceeds via a cyclic iodonium ion with good regio- and stereospecificity (anti addition). Since anhydrous HF is inconvenient for lab use, Olah suggested replacing it with the easier-to-handle HF.pyridine (eq 2).2a Many variations on this procedure have since appeared. These include the following combinations: NIS-Et3N/3HF,11 NIS-AgF/CaF2,12 NIS-Bu4NHF2,13 NIS-NH4HF2/ultrasound,14 and I(py)
Molecular IF, prepared in situ from the elements, adds across double bonds with similar results to [IF], but it also adds quite efficiently to much less reactive enones, usually with subsequent elimination of HF and resulting in the difficult-to-obtain a-iodo enones (eq 3).2b Various alkynes react as well to form a,a-difluoro-b,b-diiodo derivatives (eq 4).2c
The strong electrophilicity of the iodine in molecular IF is the driving force behind the successful iodination of various aromatic compounds. In the case of aromatic rings such as toluene, mono-, di-, or triiodo derivatives can be made at will by varying the temperature and amount of the reagent (eq 5), while with deactivated rings such as benzonitrile only the meta monoiodo derivative is obtained in high yields (eq 6).3
Iodine monofluoride has found yet another use in converting ketones, via their hydrazones, into the corresponding CF2 derivatives (eq 7).4 The reaction is general; aliphatic, alicyclic, benzylic, and steroidal carbonyls react successfully. Mono- and disubstituted hydrazones, semicarbazones, and DNPs can react as well. It should be noted that with [IF], this reaction does not give satisfactory results.16
Tel Aviv University, Israel