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K. Tanaka
~ 99% enantioselectivity in high yield (Table 23.4) [10]. A homogeneous catalyst
used as a reference showed lower activity and asymmetric induction.
23.2.4 Cyanosilylation
Cui and co-workers [11] synthesized vanadium(V)-containing cage-type (S)-MOF6 with metal–salen fragments from dicarboxylic acid 6. (S)-MOF-6 showed high
enantioselectivity in addition of trimethylsilyl cyanide to aromatic and heteroaromatic aldehydes to form the cyanohydrin silyl ether with a high ee value in the presence of 1 mol% (S)-MOF-6 (Table 23.5). They suggested that the low ee value of the
adduct obtained from anthracene-9-carbaldehyde could be related to steric hindrance.
A homogeneous catalyst prepared from dimethyl VO (salen) dicarboxylate showed
considerably lower asymmetric induction of 51% ee with 42.6% conversion.
23.2.5 Henry Reaction
Jiang et al. [12] reported synthesis of the three-dimensional (3D) chiral metallosalenbased chiral MOF [Cd 2 (Cu(salen))(DMF) 3 ]·DMF·3H 2 O (R)-MOF-7 with a onedimensional open channel. In the presence of 1 mol% (R)-MOF-7 and (i-Pr) 2 EtN as
a co-catalyst, nitromethane enantioselectively added to various aliphatic, aromatic,
and heteroaromatic aldehydes to give the corresponding (R)-adducts (Table 23.6).
For most of the reactions, the yields were high and the ee values exceeded 90%. The
exceptions were sterically hindered aldehydes, such as naphthalene-1-carbaldehyde
and anthracene-9-carbaldehyde, and 4-nitrobenzaldehyde. Pyrene-1-carbaldehyde
failed to react under the reaction conditions, presumably because of its large size,
which prevents it from accessing the catalytic sites inside the pores of (R)-MOF-7.
23.2.6 Morita–Baylis–Hillman Reaction
Hu et al. [13] reported synthesis of a chiral ionic liquid moiety of a L-pyrrolidin2-ylimidazole-decorated homochiral UiO-68-type MOF, followed by impregnating
UiO-68-type coordination polymer in a toluene solution of Ti(Oi-Pr) 4 and subsequent
hydrolysis of the latter inside MOF-8 pores. The obtained porous TiO 2 @MOF-8
composite catalyst was an efficient asymmetric heterogeneous catalyst in the Morita–
Baylis–Hillman reaction. Addition of methyl acrylate to substituted benzaldehydes
in the presence of 2 mol% TiO 2 @MOF-8 afforded the corresponding (R)-products
in high yield with excellent enantiomeric purity (Table 23.7).
K. Tanaka
~ 99% enantioselectivity in high yield (Table 23.4) [10]. A homogeneous catalyst
used as a reference showed lower activity and asymmetric induction.
23.2.4 Cyanosilylation
Cui and co-workers [11] synthesized vanadium(V)-containing cage-type (S)-MOF6 with metal–salen fragments from dicarboxylic acid 6. (S)-MOF-6 showed high
enantioselectivity in addition of trimethylsilyl cyanide to aromatic and heteroaromatic aldehydes to form the cyanohydrin silyl ether with a high ee value in the presence of 1 mol% (S)-MOF-6 (Table 23.5). They suggested that the low ee value of the
adduct obtained from anthracene-9-carbaldehyde could be related to steric hindrance.
A homogeneous catalyst prepared from dimethyl VO (salen) dicarboxylate showed
considerably lower asymmetric induction of 51% ee with 42.6% conversion.
23.2.5 Henry Reaction
Jiang et al. [12] reported synthesis of the three-dimensional (3D) chiral metallosalenbased chiral MOF [Cd 2 (Cu(salen))(DMF) 3 ]·DMF·3H 2 O (R)-MOF-7 with a onedimensional open channel. In the presence of 1 mol% (R)-MOF-7 and (i-Pr) 2 EtN as
a co-catalyst, nitromethane enantioselectively added to various aliphatic, aromatic,
and heteroaromatic aldehydes to give the corresponding (R)-adducts (Table 23.6).
For most of the reactions, the yields were high and the ee values exceeded 90%. The
exceptions were sterically hindered aldehydes, such as naphthalene-1-carbaldehyde
and anthracene-9-carbaldehyde, and 4-nitrobenzaldehyde. Pyrene-1-carbaldehyde
failed to react under the reaction conditions, presumably because of its large size,
which prevents it from accessing the catalytic sites inside the pores of (R)-MOF-7.
23.2.6 Morita–Baylis–Hillman Reaction
Hu et al. [13] reported synthesis of a chiral ionic liquid moiety of a L-pyrrolidin2-ylimidazole-decorated homochiral UiO-68-type MOF, followed by impregnating
UiO-68-type coordination polymer in a toluene solution of Ti(Oi-Pr) 4 and subsequent
hydrolysis of the latter inside MOF-8 pores. The obtained porous TiO 2 @MOF-8
composite catalyst was an efficient asymmetric heterogeneous catalyst in the Morita–
Baylis–Hillman reaction. Addition of methyl acrylate to substituted benzaldehydes
in the presence of 2 mol% TiO 2 @MOF-8 afforded the corresponding (R)-products
in high yield with excellent enantiomeric purity (Table 23.7).