Topics in Current Chemistry (2018) 376:46
1 3
Et 2 Zn (Scheme 30) [74]. The direct translation of the reaction conditions used in
batch to flow mode resulted in very high conversion at a convenient combined flow
rate. A single-pass, continuous flow process implemented with supported ligand 67
showed only a marginal decrease in conversion after 30 h of continuous operation.
In one single continuous flow operation, enantiopure alcohol 68 was isolated with a
TON of 251 and a productivity of 6.4 mmol h
−1
g
−1
resin . The recorded TON represents
a tenfold increase with respect to the recycling tests and a 30-fold increase compared
to batch conditions. The residence time, under these flow conditions, was in sharp
contrast to the required time for full conversion at the same temperature under batch
conditions (6 h).
Harada reported recently that silica-supported BINOL ligand 69 was used for
the enantioselective arylation of aldehydes under continuous flow conditions [75].
The silica-supported BINOL 69 exhibited high performance in the enantioselective
arylation of aromatic aldehydes using Grignard reagents (Scheme 31). Even with
a simple pipet reactor packed with the heterogeneous ligand, the enantioselective
production of chiral diarylmethanols 70 could be achieved through a continuous
introduction of aldehydes and mixed titanium reagents generated from the organometallic precursors. The synthetic potential of the silica-supported ligand was further indicated by the fact that the pipet reactor could be used repeatedly in different
reactions without appreciable deterioration of the activity.
Luis reported macroporous monolithic miniflow reactors containing the Ru-pybox
catalyst 71 (Scheme 32) for the asymmetric cyclopropanation under continuous flow
conditions [76, 77]. The corresponding ruthenium complex 71 was tested for the
continuous flow cyclopropanation reaction between styrene and ethyldiazoacetate
Scheme 31 Enantioselective arylation of aldehydes using a pipet reactor packed with supported ligand
69
56
Reprinted from the journal
1 3
Et 2 Zn (Scheme 30) [74]. The direct translation of the reaction conditions used in
batch to flow mode resulted in very high conversion at a convenient combined flow
rate. A single-pass, continuous flow process implemented with supported ligand 67
showed only a marginal decrease in conversion after 30 h of continuous operation.
In one single continuous flow operation, enantiopure alcohol 68 was isolated with a
TON of 251 and a productivity of 6.4 mmol h
−1
g
−1
resin . The recorded TON represents
a tenfold increase with respect to the recycling tests and a 30-fold increase compared
to batch conditions. The residence time, under these flow conditions, was in sharp
contrast to the required time for full conversion at the same temperature under batch
conditions (6 h).
Harada reported recently that silica-supported BINOL ligand 69 was used for
the enantioselective arylation of aldehydes under continuous flow conditions [75].
The silica-supported BINOL 69 exhibited high performance in the enantioselective
arylation of aromatic aldehydes using Grignard reagents (Scheme 31). Even with
a simple pipet reactor packed with the heterogeneous ligand, the enantioselective
production of chiral diarylmethanols 70 could be achieved through a continuous
introduction of aldehydes and mixed titanium reagents generated from the organometallic precursors. The synthetic potential of the silica-supported ligand was further indicated by the fact that the pipet reactor could be used repeatedly in different
reactions without appreciable deterioration of the activity.
Luis reported macroporous monolithic miniflow reactors containing the Ru-pybox
catalyst 71 (Scheme 32) for the asymmetric cyclopropanation under continuous flow
conditions [76, 77]. The corresponding ruthenium complex 71 was tested for the
continuous flow cyclopropanation reaction between styrene and ethyldiazoacetate
Scheme 31 Enantioselective arylation of aldehydes using a pipet reactor packed with supported ligand
69
56
Reprinted from the journal