Recently, a new approach to activate small molecules known as the frustrated Lewis pairs (FLPs) concept has been introduced. In general, FLPs are based on a sterically hindered Lewis acid and a Lewis base which cannot interact and form the Lewis adduct. They are, therefore, highly reactive and even capable of heterolysis of H2 and thus generate onium borohydrides.[1, 2]
We introduced ansa-aminoboranes as a class of compounds that hold a Lewis acid and a Lewis base functionalities in the same molecule. Holding a FLP reactivity, ansa-aminoboranes are efficient catalysts for heterolytic splitting of H2 and for further development of catalytic applications. The amine, borane and bridging moiety of the ansa-aminoboranes can be greatly varied giving rise to structures with reversible hydrogen activation and advanced catalytic properties including high reactivity and enantioselectivity in hydrogenation of imines and enamines. In the series of ansa-aminoboranes, 2-[bis(penta-fluorophenyl)boryl]-N,N-dimethylaniline is unique and catalyzes facile hydrogenation of alkynes to cis-alkenes under mild conditions. During hydrogenation the catalyst makes use of several elementary steps including hydroboration and heterolytic H2 splitting. This reactivity pattern serves as a platform for development of various catalytic reactions including C–H borylation.[5, 6]
- For a review, see D. W. Stephan, Science, 354, 1248, (2016).
- V. Sumerin et al., Angew. Chem., Int. Ed., 47, 6001 (2008).
- V. Sumerin et al., J. Am. Chem. Soc., 130, 14117 (2008).
- K. Chernichenko, et al., Nat. Chem., 5, 718-723 (2013).
- K. Chernichenko, et al. J. Am. Chem. Soc., 138, 4860 (2016).
- M.-A. Légaré, et al., Science, 349, 513, (2015).