Biphasic techniques, comparison

In comparison with classical processes involving thermal separation, biphasic techniques offer simplified process schemes and no thermal stress for the organometal-lic catalyst. The concept requires that the catalyst and the product phases separate rapidly, to achieve a practical approach to the recovery and recycling of the catalyst. Thanks to their tunable solubility characteristics, ionic liquids have proven to be good candidates for multiphasic techniques. They extend the applications of aqueous biphasic systems to a broader range of organic hydrophobic substrates and water-sensitive catalysts [48-50]. 

Comparison with Phase-Transfer, Micellar and Other Biphasic Techniques... 

A drawback of the aqueous protocol in the Suzuki reaction is the possibility of protonolysis, which sometimes happens with sterically hindered boronic acids, in which case the rate of cross-coupling reaction may become lower than the rate of side reactions. Thus, in the reaction of methyl 5-bromonicotinate with sterically hindered o-tolylboronic acid, the use of a biphasic technique with Na2C03 as a base gave poor results in comparison with the reaction in anhydrous DMF in the presence of EtsN (Scheme 37). " ... 

Similarly, in the reaction of methyl 5-bromonicotinate with sterically hindered o-tolylboronic acid, the use of the biphasic technique with Na2C03 as a base gave poor results in comparison with the reaction in anhydrous DMF in the presence of Et3N [38] ... 

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