Boron-Based Lewis Acid Catalysis: Challenges and Perspectives

Abstract

In the last two decades, boron-based catalysis has been gaining increasing traction in the field of organic synthesis. The use of halogenated triarylboranes as main group Lewis acid catalysts is an attractive strategy. It has been applied in a growing number of transformations over the years, where they may perform comparably or even better than the gold standard catalysts. This review discusses methods of borane synthesis and cutting-edge boron-based Lewis acid catalysis, focusing especially on tris(pentafluorophenyl)-borane [B(C6F5)3], and other halogenated triarylboranes, highlighting how boron Lewis acids employed as catalysts can unlock a plethora of unprecedented chemical transformations or improve the efficiency of existing reactions.

Mapping boron catalysis onto a phosphorus cluster platform

“…[7][8][9][10] Boron centered catalysts are particularly exciting because they are sustainable environmentfriendly alternatives to expensive transition metal catalysts, based on their higher crustal abundance and lower costs. [11][12][13][14][15] Zintl clusters, clusters of main group elements, can be understood as molecular prototypes of heterogenous materials. 16 Heptaphosphane ([P 7 ]) clusters are particularly interesting because they are structural fragments of red phosphorus.…”

Activation of Small Molecules and Hydrogenation of CO2 Catalyzed by Frustrated Lewis Pairs

“…There are a few mechanistic paths of H2 activation by FLPs reported in the literature, proposed by various scientists over the years. A mechanistic path, proposed by Welch and Stephan in 2007, describes an initial polarization of H2 occurring as a result of a side-on interaction between H2 and the LA (B(C6F5)3) forming the adduct, H2…B(C6F5)3 [36,51], from which a phosphine LB (PtBu3) abstracts a proton (mechanism shown in Figure 1a). Unfortunately, no such adduct is detected experimentally even at higher H2 pressure (4 atm).…”

“…. B(C 6 F 5 ) 3 [36,51], from which a phosphine LB (PtBu 3 ) abstracts a proton (mechanism shown in Figure 1a). Unfortunately, no such adduct is detected experimentally even at higher H 2 pressure (4 atm).…”

Borane-catalyzed dehydrogenative C–C bond formation of indoles with N-tosylhydrazones: an experimental and computational study

“…Over the last decade, metal-free main group catalysis has gained significant attention to unravel new reactivity and selectivity over the classical transition-metal catalysis. [39][40][41][42][43][44][45] To date a series of boron based Lewis acid catalysts have been known in the main group chemistry, out of which tris( pentafluorophenyl)borane (B(C 6 F 5 ) 3 ) has evolved as the most versatile catalyst. [46][47][48] The inherent electrophilic character and strong Lewis acidity have increased its applications in various transformations including cyclization, 49-53 dehydrogenation, [54][55][56][57] hydrosilylation, [58][59][60][61] hydroboration, 62,63 and Frustrated Lewis Pair (FLP) chemistry [64][65][66][67][68] for activation of small molecules.…”