Polystyrene-Supported TRIP: A Highly Recyclable Catalyst for Batch and Flow Enantioselective Allylation of Aldehydes

Abstract

The widely applicable TRIP phosphoric acid catalyst has been immobilized on polystyrene using a copolymerization-based strategy. The resin (PS-TRIP) has proven to be highly active and enantioselective in the asymmetric allylboration of aldehydes. Moreover, it has shown to be extremely robust, as it can be reused for 18 times, after which it still retained its activity. Lastly, to further prove the benefits of the immobilization, a continuous flow experiment spanning 28 h has been carried out with very high yields and ee's.

Catalytic Enantioselective Flow Processes with Solid‐Supported Chiral Catalysts

“…The batch experiments worked smoothly to generate 18 different allylated products re‐using the same sample of 22 . Basic substrates deactivated the catalyst (presumably by acid‐base reaction) but, as with 21 , the activity could be restored by washing the resin with HCl in EtOAc …”

“…Basic substrates deactivated the catalyst (presumably by acid-base reaction) but, as with 21, the activity could be restored by washing the resin with HCl in EtOAc. [81] The flow process was carried out with two independent pumps due to the incompatibility of the aldehyde and the allylboronate. Downstream of the column, a third pump fed the system with aqueous NaHSO 3 to scavenge the remaining aldehyde; otherwise, a background process took place, drastically reducing the recorded enantioselectivities (Figure 19).…”

An Integrated Lab‐on‐a‐chip Approach to Study Heterogeneous Enantioselective Catalysts at the Microscale

“…The immobilization of catalysts to solid supports is particularly important with respect to enantioselective catalysis. [1][2][3][4][5][6] Different immobilization strategies involve a wide variety of molecular species and support materials. [7][8][9][10] The catalytic performance of an active material is strongly dependent on the nature of the catalyst, the solid support, the immobilization strategy as well as the use of various spacers to maintain the catalytic activity of the bound molecules.…”

A Versatile Bis‐Allylboron Reagent for the Stereoselective Synthesis of Chiral Diols

“…NaOH, MeOH, RT or filtration over silica gel (63 %);c )TBSCl, N,N-dimethylformamide, RT; then THF, aq. [26] The a,b-unsaturated cinnamaldehyde ( Table 1, entry 13) reacted with excellent yield and good enantioselectivity (86 % ee), while very high enantioselectivities were obtained for the linear aliphatic 3-phenylpropionaldehyde and the abranched cyclohexanecarbaldehyde ( Table 1, entries 10 and 12). NaOH, H 2 O 2 ,08 8CtoRT(71 %o ver two steps);e )TBSCl, CH 2 Cl 2 ,R T; (76 %over two steps);f)9-Borabicyclo(3.3.1)nonane, THF, then aq.…”

“…In line with previous observations, aldehydes bearing ab asic nitrogen atom (2-pyridiyl and 2quinolyl) gave racemic products as ar esult of acid-base reaction with the acid catalyst (not shown). [26] The a,b-unsaturated cinnamaldehyde ( Table 1, entry 13) reacted with excellent yield and good enantioselectivity (86 % ee), while very high enantioselectivities were obtained for the linear aliphatic 3-phenylpropionaldehyde and the abranched cyclohexanecarbaldehyde ( Table 1, entries 10 and 12). On the other hand, the b-branched and sterically less demanding isovaleric aldehyde (entry 11) gave the desired product in 73 % ee.…”