Recycling Asymmetric Hydrogenation Catalysts by Their Immobilization onto Ion‐Exchange Resins

Abstract

Ion-exchange resins can be used as supports for the preparation of single-site, heterogenised asymmetric hydrogenation catalysts. The immobilised catalysts obtained can be efficiently and conveniently recovered and recycled. This article reviews the significant contributions in the field including the main concepts behind the design and the applications of this type of catalyst.

Simple and Efficient Recyclable Catalytic System for Performing Copper‐Catalysed S‐Arylation Reactions in the Presence of Water

“…As shown in Figure 2, it is possible to use the water solutions containing the copper complexes three times with hardly any variation in the yields of the target compounds. However, after the third use a change of colour in the water solutions from the original violet to brown was observed, and the utilisation of such brown aqueous solution to perform the fourth run of each reaction resulted in a clear decrease in the yields of both sulfides 3 d and k 13…”

Noncovalently Supported Heterogeneous Chiral Amine Catalysts for Asymmetric Direct Aldol and Michael Addition Reactions

“…The catalyst with a high loading of 2.75 mmol g À1 was totally inactive ( Table 2, entry 7). Other types of PS/sulfonic acids, such as 3 appended with a long alkyl chain and linear 4, gave poor results ( Table 2, entries [8][9][10][11]. Notably, the catalysis of 1 e/2 d could be significantly accelerated using much less solvent ( Table 1, entry 6 versus 5).…”

“…In fact, a similar strategy of noncovalently attaching transition-metal catalysts onto solid supports has been previously well explored with good activity and reusability. [9] Recently, an acid-base strategy was applied to immobilize ruthenium cross-metathesis catalysts, thus leading to enhanced activity. [10] Our design herein is distinct from these previous reports as a result of the dual functions of the solid-acid supports: first, they act as an anchor for the chiral diamines and second they act as a critical modulator for the catalytic activity and stereoselectivity (Scheme 1).…”

Development of a Continuous‐Flow System for Asymmetric Hydrogenation Using Self‐Supported Chiral Catalysts

“…Although BET measurements suggest a nonporous material for the present self‐assembled metal–organic polymers, this precatalyst condition might very well change in solution under hydrogenation conditions. As observed in a number of polymer (cross‐linked) or resin‐bound catalyst systems,3b, 4a, g, i a nonporous polymer would be expected to undergo swelling in the reaction solvent. However, as can be seen in Figure 5, changing the stirring (and mixing) time prior to H 2 activation did not result in any significant change to the overall reaction profile shape.…”