Applications of boron compounds in catalysis

In recent years, metal-free catalysis has gained attention owing to its nontoxicity. Boron-based molecules play an important role in metal-free catalysis. An overview of triaryl or mixed aryl-alkylboranes, diarylborane, monoarylboranes, and borocations in catalysis is presented in this chapter. Lewis acidity and stability of trivalent boron compounds, especially tris(pentafluorophenyl)borane, made it as an increasingly useful catalyst in various organic transformations such as hydrogenation, hydrosilylation, hydroboration, reductive amination, N-alkylation, and so on. Apart from the Lewis acidity, borinic and boronic acids have the tendency to form reversible covalent interaction with groups such as carboxyl, hydroxyl, and carbonyl groups, which help them to activate the reagents in various organic transformations. Another important family of boron-based catalysis is borocation. Borocation, especially oxazaborolidines, plays a vital role in asymmetric catalysis such as Diels–Alder reaction, Michael addition, [3+2] cycloaddition, [2+2] cycloaddition, cyanosilylation of carbonyl compounds, etc. At the end of this chapter, the miscellaneous reactions catalyzed by boron reagents are summarized to illustrate the significance of boron catalysis.