1 Frustrated Lewis Pair Catalysis: An Introduction
11
and soluble N-donor act as a rare example of a biphasic FLP which is able to activate
H 2 .
In 2018, Ma and coworkers developed a clever strategy to install a Lewis pair in
the pores of a metal-organic framework (MOF). These authors [83] then went on to
employ this MOF–FLP material to affect the reduction of various imines. Moreover,
these materials were shown to be recyclable in subsequent reduction runs. This
strategy offers the advantages of air stability and recyclability of the catalyst while
selectivity can be tuned via the manipulation of the MOF-FLP pore-size [83, 84].
In a subsequent study, Ma’s groups extended the utility of such MOF-FLP catalysts
to affect the heterogeneous reduction of αβ-unsaturated organic compounds. For
example, this catalyst was capable of selectively reducing the imine bond in αβunsaturated imine substrates en route to the allylic amines [85].
1.2.6 Asymmetric Hydrogenation
The evolution from a broadening scope of substrates to more sophisticated catalyst systems capable of stereoselective reductions is a path that began for transition
metal chemistry some 50 years ago. A similar evolution has occurred for FLP catalysts. Indeed, the potential of stereoselective, metal-free hydrogenations by FLPs
was recognized very early on, as Klankermayer [86] reported such reduction in
2008, albeit with poor enantioselectivity. Nonetheless, efforts toward this end have
continued, with contributions from our group as well as those of Erker [87] and Repo
[88]. While Repo’s system was certainly the best of these, the indisputable leader in
the development of asymmetric FLP reduction catalysts has been the research group
of Du [89–92] while Wang and coworkers [93] have more recently made important
contributions. Details of these systems are reviewed in a subsequent chapter and thus
further discussion of these important advances is not present here.
1.3 Other Catalysis with FLPs
The ability of FLPs to activate H 2 also probed immediate questions about the possibility of the activation of other small molecules. Indeed, a great deal of work has
been done based on this concept, and much of the stoichiometric chemistry has been
reviewed previously. Here, we describe the key examples where such small molecule
activation by FLPs can be applied in the catalysis.
11
and soluble N-donor act as a rare example of a biphasic FLP which is able to activate
H 2 .
In 2018, Ma and coworkers developed a clever strategy to install a Lewis pair in
the pores of a metal-organic framework (MOF). These authors [83] then went on to
employ this MOF–FLP material to affect the reduction of various imines. Moreover,
these materials were shown to be recyclable in subsequent reduction runs. This
strategy offers the advantages of air stability and recyclability of the catalyst while
selectivity can be tuned via the manipulation of the MOF-FLP pore-size [83, 84].
In a subsequent study, Ma’s groups extended the utility of such MOF-FLP catalysts
to affect the heterogeneous reduction of αβ-unsaturated organic compounds. For
example, this catalyst was capable of selectively reducing the imine bond in αβunsaturated imine substrates en route to the allylic amines [85].
1.2.6 Asymmetric Hydrogenation
The evolution from a broadening scope of substrates to more sophisticated catalyst systems capable of stereoselective reductions is a path that began for transition
metal chemistry some 50 years ago. A similar evolution has occurred for FLP catalysts. Indeed, the potential of stereoselective, metal-free hydrogenations by FLPs
was recognized very early on, as Klankermayer [86] reported such reduction in
2008, albeit with poor enantioselectivity. Nonetheless, efforts toward this end have
continued, with contributions from our group as well as those of Erker [87] and Repo
[88]. While Repo’s system was certainly the best of these, the indisputable leader in
the development of asymmetric FLP reduction catalysts has been the research group
of Du [89–92] while Wang and coworkers [93] have more recently made important
contributions. Details of these systems are reviewed in a subsequent chapter and thus
further discussion of these important advances is not present here.
1.3 Other Catalysis with FLPs
The ability of FLPs to activate H 2 also probed immediate questions about the possibility of the activation of other small molecules. Indeed, a great deal of work has
been done based on this concept, and much of the stoichiometric chemistry has been
reviewed previously. Here, we describe the key examples where such small molecule
activation by FLPs can be applied in the catalysis.