## 2 Results
In addition to possessing dipole moment, the presence of water is also beneficial due to increased amount of hydrophilic boronates RB(OH)\({}_{3}\)-[31]. Overall, solvent mixture of 1,4-dioxane and H\({}_{2}\)O in ratio 2:1 appeared to be the most optimal, with 80% yield. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Entry** & **Catalyst (_ligand_)** & \multicolumn{3}{c}{**Yield (\%) 1,2**} & \multicolumn{1}{c}{**Selectivity Ratio 3:4 3**} \\  & **1 h** & **2 h** & **24 h** & \\ \hline
1 & Pd\({}_{2}\)dba\({}_{3}\) & 0 & 0 & 2 & / \\
2 & Pd\({}_{2}\)dba\({}_{3}\cdot\) CHCl\({}_{3}\) & 15 & 21 & 35 & 5 \\
3 & Pd\({}_{2}\)dba\({}_{3}\) (_TTBP \(\cdot\) HBF\({}_{4}\)_) & 10 & 11 & 23 & 11.5 \\
4 & PdCl\({}_{2}\)(PPh)\({}_{2}\) & 12 & 17 & 36 & 4.5 \\
5 & Pd(OAc)\({}_{2}\) (_PCy3)\({}_{2}\)_ & 10 & 12 & 26 & 13 \\
6 & Pd(OAc)\({}_{2}\) (_PPh3\({}_{2}\)_) & 28 & 37 & 46 & 10 \\
7 & Pd(OAc)\({}_{2}\) (_PPh3 on DVB_)\({}_{2}\) & 15 & 22 & 27 & 7 \\
8 & Pd(dppf)Cl\({}_{2}\cdot\) CH\({}_{2}\)Cl\({}_{2}\) & 26 & 38 & 70 (63) 4  & 10 \\
9 & Pd(PPh)\({}_{4}\) & 29 & 41 & 72 (71) 4  & 9 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Catalyst screening for Suzuki coupling of **1** with **2**. A scan of minimal solvent volume of 1,4-dioxane/ H\({}_{2}\)O (2:1) was performed (see Supporting Information, Table S3). Initial total volume of 6 mL in addition to 4.5 mL were found as the most suitable, while the yield significantly decreased when smaller solvent volumes were used. All further experiments were performed in total volume of 6 mL. Microwave-assisted reaction conditions, i.e., temperature and time, were further evaluated. First, the reaction mixture was subjected to temperature scan ranging from 60 \({}^{\circ}\)C to 140 \({}^{\circ}\)C with the interval of 20 \({}^{\circ}\)C (Table 4). The temperature of 100 \({}^{\circ}\)C appeared to be the most optimal leading to 80% yield. Higher temperatures (i.e., 120 \({}^{\circ}\)C and 140 \({}^{\circ}\)C, entries 7 and 10, respectively) did not improve the yield, since the side product 2,4-diphenylpyrimidine was formed. Additionally, time of the reaction was monitored for temperatures equal or above 100 \({}^{\circ}\)C. Reaction time of 15 min at 100 \({}^{\circ}\)C (yield 81%, entry 4) was found as equally efficient as 20 min. Therefore, these conditions were used for all further reactions. To investigate the optimal amount of catalyst needed for the microwave-assisted Suzuki coupling, we performed the scan of catalyst loading, ranging from 5 mol% to 0.05 mol%. Contrary to the results from the experiments, performed in a flask, the minimal amount of catalyst needed for microwave-assisted reaction was only 0.5 mol% (Table 5), with lower amounts shown to be insufficient for all starting material to react. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Entry** & **Temperature [\({}^{\circ}\)C]** & **Time [min]** & **Yield (\%) 1,2** \\ \hline
1 & 60 & 20 & 12 \\
2 & 80 & 20 & 60 \\
3 & 100 & 20 & 80 \\
4 & 100 & 15 & 81 \\
5 & 100 & 10 & 59 \\
6 & 100 & 5 & 46 \\
7 & 120 & 20 & 60 \\
8 & 120 & 10 & 61 \\
9 & 120 & 5 & 66 \\
10 & 140 & 20 & 56 \\
11 & 140 & 5 & 61 \\ \hline \hline \end{tabular} \({}^{1}\) Reaction conditions: **1** (75 mg, 0.50 mmol), 1,4-dioxane (4 mL), H\({}_{2}\)O (2 mL), K\({}_{2}\)CO\({}_{3}\) (207 mg, 1.50 mmol), **2** (61 mg, 0.50 mmol), Pd(PPh)\({}_{4}\) (17.3 mg, 0.015 mmol, 3 mol%), MW, _temperature_, _time_. 2 Yield for 3, determined by LC-MS.  
\end{table} 
Table 4: Temperature and time screening for Suzuki coupling of **1** with **2**. \begin{table}