Supported Ionic Liquid Catalysis SILC

The Sharpless AE of allylic alcohols has become a benchmark classic in catalytic asymmetric synthesis [52a,b] and has found use in some industrial applications [52c]. Although this catalytic process seems to be well understood, a heterogeneous system would be advantageous as it could avoid a complicated separation of the product from the catalyst, which can lead to decomposition of the epoxide formed [52c]. However, only a few heterogeneous versions of this important reaction have been conducted successfully [43, 51c, 53]. 

Using PLL-Si (hetero), 95% ee and 90% yield Using PLL (homo), 95% ee (45% yield) 

Using PLN-Si (hetero), 97% ee (100% yield) Using PIN (homo), 90% ee (97% yield) 

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The hydroformylation of 1-hexene by supported ionic liquid catalysis (SILC) was recently reported by researchers at ExxonMobil. In this system, the active catalyst HRh(CO)(tppti)3 (tppti = tri(m-sulfonyl)triphenyl phosphine tris(l-butyl-3-methyl-imidazolium)) is contained within the ionic liquid phase while excess tppti ligand is immobilized in the support material. TOP values of 65 min" were obtained with silc while an unsupported biphasic ionic liquid medium gave TOP values of 23 min. ... 

Gruttadauria et al. [71a] utilized the previously described supported ionic liquid catalysis (SILC) concept for the L-proline-catalyzed aldol reaction (Scheme 2.33). 

Attachment to the Support via SILC or SILP Catalysis Supported, ionic liquid catalysis (SILC) or supported, ionic hquid-phase (SILP) catalysis involves the incorporation of an organometalhc complex in an IE and the subsequent immobilization or confinement within the pores of an inorganic support [83]. This is an attractive... 

This section summarizes the recent progress in supported ionic hquid catalysis, demonstrating synthetic apphcations where the ionic liquid can play its role as either iimocent solvent (SILP) or the catalyst itsdf (SILC), depending on the specific cation/anion combination and the reaction under investigation. 

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