## 2 Results and Discussion
### Biphasic Sequestration of Pd and Cu from Products of Catalytic Reactions  
As noted in the introduction, metal sequestration and separation from products is especially important in catalytic reactions where the catalysts end up in a product phase. Our results in Tables 1 and 2 suggest that the soluble polymer bound sequestrant **1** should be useful in these cases. To explore this question, we studied the use of **1** for removal of the Pd residues from Suzuki cross-coupling and Buchwald-Hartwig amation reactions (Scheme 2). Similar studies were also carried out for a CuAAC reaction. \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Pd complex**} & \multicolumn{2}{c}{**Contents/ppm 1**} & \multicolumn{2}{c}{**Efficiency/\%**} \\ \cline{2-5}  & **in 4 h** & **in 12 h** & **in 4 h** & **in 12 h** \\ \hline (PPH\({}_{3}\))\({}_{2}\)Pd(OAc)\({}_{2}\) & 0.620 & 0.39 & 98.8 & 99.2 \\ (P(o-Anisyl)\({}_{3}\))\({}_{2}\)Pd(OAc)\({}_{2}\) & 6.36 & 3.17 & 87.3 & 93.7 \\ (P(o-Tolyl)\({}_{3}\))\({}_{2}\)Pd(OAc)\({}_{2}\) & 6.03 & 1.94 & 87.9 & 96.1 \\ (PCy)\({}_{3}\))\({}_{2}\)Pd(OAc)\({}_{2}\) & 0.610 & 0.560 & 98.8 & 98.9 \\ (RuPhoS)\({}_{2}\)Pd(OAc)\({}_{2}\) & 9.24 & 2.01 & 81.5 & 96.0 \\ (DPPF)Pd(OAc)\({}_{2}\) & 10.2 & 2.67 & 79.5 & 94.7 \\ (DPFhoS)Pd(OAc)\({}_{2}\) & 2.08 & 1.02 & 95.8 & 98.0 \\ (XrDhoS)Pd(OAc)\({}_{2}\) & 0.820 & 0.440 & 98.4 & 99.1 \\ Pd\({}_{2}\)(dba)\({}_{3}\)\({}_{2}\) & 2.65 & 1.47 & 97.3 & 98.5 \\ (C\({}_{6}\)H\({}_{5}\)CN)\({}_{2}\)PdCl\({}_{2}\) & 0.430 & 0.430 & 99.3 & 99.1 \\ (CH\({}_{3}\)CN)\({}_{2}\)PdCl\({}_{2}\) & 0.310 & 0.190 & 99.4 & 99.6 \\ Herrmann’s catalyst & 8.05 & 5.19 & 83.9 & 89.6 \\ \hline \hline \end{tabular}  
* 6 eq. of **1** were used for extraction.  
\end{table} 
Table 2: Results of competitive sequestration of palladium complexes from acetonitrile solutions. Reaction of phenyl boronic acid **3** with different substituted bromoarenes under typical coupling conditions using 2.5 mol% of Pd(OAc)\({}_{2}\) afforded biaxyls **4a-c** in toluene (Scheme 2). The crude products **4a** and **4b** (dark brown) contained 275 ppm of Pd as measured by ICP-OES. However, when the crude products were dissolved in MeOH and shaken for 4 h with a 6-fold excess of **1** in a heptane solution, complete discoloration of the MeOH phase was observed as depicted in Figure 2. Quantitative ICP-OES analysis of the treated product showed that the Pd concentration decreased by 99.9 % (Table 3). However, in the case of the reaction leading to **4c**, the Pd recovery under the same biphasic conditions was not as efficient due to its poor solubility. A separate experiment where **1** was allowed to interact with the crude product mixture under homogeneous conditions led to three order of magnitude decrease of Pd contents. In this case the crude **4c** was mixed with 6-fold excess of **1** in DCM and stirred at ambient temperature for 2 h. After solvent removal, the desired 4-methoxybisphenyl **4c** was isolated by liquid-liquid fractionation in MeOH-heptane 1:1 (_v/v_) mixture. Bromobenzene and 2-bromopyridine were successfully coupled to morpholine under neat conditions using 1 mol% of Pd(OAc)\({}_{2}\) and RuPhos as a ligand to afford compounds **6a** and **6b**. Again, a high level of removal of the Pd residues from the final product was achieved under biphasic conditions. A third example of this reaction that led to formation of N-(4-anisyl)piperazine **6c** was slightly less successful and afforded only 63% Pd sequestration at ambient temperature. As was true for the methoxybisphenyl **4c** example above, this poor sequestration efficiency was presumed to result from the modest solubility of the crude product in the solvent mixture. In this case, heating the biphasic mixture of acetonitrile solution of the product **6c** and heptane solution of **1** at 80 \({}^{\circ}\)C for 4 h led to 96.9% sequestration of the Pd catalyst residue. Figure 2: Qualitative visual photographs showing the results of Pd sequestration from crude compounds **4a,b**.