Introduction
<P>Reactions in the presence of Lewis acids are commonplace in modern synthetic chemistry.
[
1]
Pentafluorophenylborane compounds were first reported in the 1960s by Chambers
[
2]
and Massey but their strong Lewis acidity was unexploited until the 1980s when Paetzold
and co-workers generated monomeric iminoborane which undergoes cycloaddition reactions
with nitriles or isonitriles (Equation 1).
[
3]
Since then, their application in catalysis has increased tremendously.
[
4]
Tris(pentafluorophenyl)borane has emerged as a powerful but selective reagent in many
organic transformations.
[
5]
Due to its uniqueness, it is a ubiquitous component of many important alkyl-based
olefin polymerization catalysts and functions in non-traditional Lewis acid catalyzed
reactions involving reduction of alcohols, cleavage of aryl and alkyl ethers, nonactivated
aziridines
[
6]
and epoxides. Furthermore, it catalyzes hydrosilylation of aromatic aldehydes, ketones,
ethers,
[
7]
and imines.
[
8]
Tris(pentafluorophenyl)borane is commercially available but various methods have been
developed over the years for its preparation. One preparation involves the formation
of a pentafluorophenyl metal (Group 11 or 12), followed by treatment with a boronhalide.
[
9]
</P>
Equation 1
