Preparation of Iodonium Tetrafluoroborates June 26, 2008
Posted by gaussling in Chemical Industry, Chemistry, Chemistry Blogs, Science.trackback
An interesting bit of chemistry was published by Berit Olofsson at Stockholm University in a recent JOC. The Olofsson lab has previously produced a method for the one-pot preparation of diaryliodonium triflates. This latest work provides diaryliodonium tetrafluoroborates (JOC, 2008, 73, 4602-4607).
The preparation of I(III) compounds usually starts with an Ar-I compound undergoing oxidation followed by an electrophilic addition/substitution to another arene. Regioselectivity is obtained by choosing a donor with a leaving group such as a boronic acid, stannane, or silane.
What is clever about this process is the fact that a BF4 salt is directly produced. Two equivalents of boron trifluoride etherate are used in the reaction which evidently results in some kind of disproportionation producing the BF4 counter-anion.
It is known that the reactivity of iodonium compounds is somewhat sensitive to the coordinating ability of the counter-anion, so BF4 is less undesirable than other choices (like chloride). Solubility is greatly influenced by the choice of counter-anion as well. This is particularly true in photo-initiator applications where the choice of carrier fluid may be limited.
Why stop at I(III)? I(VII) is 233% better! The most romantic hypervalent iodine compound must assuredly be fluxional structure I(CF3)_7 – and not just because it will be gaseous near room temp, MW = 609.946. Putatively from IF_7 re US Pat. 3992424, 395458 .
Berit min älskling, varför ville du att jag skulle sätta mig in detta?
Det här är inte mitt område what so ever ha, ha! Men kul att du gör väsen av dig och sluta inte att engera mig i allt du gör för den skull….
Mvh
Janne Herrström
Hello Jan, I’m sure your point is a good one (?), but since I don’t speak Scandahoovian it’s completely lost on me.