Synthetic Applications of Tris(pentafluorophenyl)borane

Abstract

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]