## 2 Experimental
### Synthesis of Tert-butyl-3-(2-furyl)-1H-indazole-1-carboxylate (Compound **5**)  
As shown in Scheme 1, compound **5** was obtained through a Pd-catalyzed Suzuki-Miyaura coupling reaction, which is comprehensively described in Section 2.11. Yellow oils (yields of 5-95%, Table 1 and Figure 2). \({}^{\mathrm{1}}\)H NMR (400 MHz, CDCl\({}_{3}\)) \(\delta_{\mathrm{H}}\), ppm: 1.77 (9H, s, _tert_-butyl), 7.41 (1H, d, \(l\) = 8.0 Hz, ArH), 7.49-7.51 (3H, m, ArH), 7.54-7.59 (2H, m, \(H\) on furyl), 8.21 (1H, t, \(l\) = 9.2 Hz, \(H\) on furyl) (Figure S7, Section S7, Supplementary Materials). \({}^{13}\)C NMR (101 MHz, CDCl\({}_{3}\)) \(\delta_{\mathrm{C}}\), ppm: 149.35, 147.77, 143.61, 141.63, 140.61, 129.19, 124.14, 123.41, 122.12, 114.81, 111.81, 110.16, 85.16, 28.25 (Figure S8, Section S8, Supplementary Materials). ESI-HRMS (positive, _m/z_): 307.1028 (Calcd. for [M+Na]\({}^{+}\) 307.2989) (Figure S9, Section S9, Supplementary Materials). Anal. Calcd for C\({}_{16}\)H\({}_{16}\)N\({}_{2}\)O\({}_{3}\): C, 67.60; H, 5.63; N, 9.86. Found: C, 68.21; H, 6.22; N, 9.25. FT-IR (KBr) \(\sigma\), cm\({}^{-1}\): 3156 (m, furyl), 2972 (m, methyl on _tert_-butyl), 1738 (vs, C=O), 1614 (m, C=N), 1510 (m, furyl), 1422 (m, furyl), 1374 (vs, C-N), 1243 (vs, C-O) (Figure S10, Section S10, Supplementary Materials).  
\begin{table}
\begin{tabular}{l l l l l} \hline \hline
**Entry a** & **Catalyst b** & **Solvent** & **Conversion (\%) c** & **Yield (\%) d** \\ \hline
1 & Pd(PPh\({}_{3}\))4 & THE a & 5 & 5 \\
2 & & BMImBF\({}_{4}\)/THE & 21 & 21 \\
3 & & BMImPF\({}_{6}\)/THE & 23 & 23 \\
4 & Pd(OAc)\({}_{2}\) & THE & 34 & 34 \\
5 & & BMImBF\({}_{4}\)/THE & 51 & 51 \\
6 & & BMImPF\({}_{6}\)/THE & 42 & 42 \\
7 & PdCl\({}_{2}\) & THE & 19 & 19 \\
8 & & BMImBF\({}_{4}\)/THE & 55 & 55 \\
9 & & BMImPF\({}_{6}\)/THE & 40 & 40 \\
10 & PdCl\({}_{2}\)(dppf) & THE & 85 & 85 \\
11 & & BMImBF\({}_{4}\)/THE & 95 & 95 \\
12 & & BMImPF\({}_{6}\)/THE & 79 & 79 \\
13 & PdCl\({}_{2}\)(dtbpf) & THE & 90 & 90 \\
14 & & BMImBF\({}_{4}\)/THE & 88 & 88 \\
15 & & BMImPF\({}_{6}\)/THE & 82 & 82 \\ \hline \end{tabular}  
* Reaction conditions (details as in Section 2.11): electrophophile **3** (1.0 mmol), nucleophilic **4** (1.2 mmol), Pd catalyst (4 mol\({}^{\circ}\), based on organic halide), THE solvent system (Toluene, 4 mL; \({}_{2}\)O, 2 mL; EtOH, 1 mL), Na\({}_{2}\)CO\({}_{3}\) (2 mmol), ILs (BMImPF\({}_{6}\), or BMImBF\({}_{4}\), 5 mL); 80 \({}^{\circ}\)C, 8 h. b \({}^{\circ}\)Pd(PPh\({}_{3}\))4, tetrakis(triphenylphosphine) palladium(0); Pd(OAc)\({}_{2}\); palladium(II) acetate; PdCl\({}_{2}\), palladium(II) chloride; PdCl\({}_{2}\)(dppf), 1\({}^{1}\)-bis(diphenylphosphine) ferrocene-palladium(II)dichloride dichloromethane; PdCl\({}_{2}\)(dtbpf), 1\({}^{1}\)-bis(di-tert-butyl)phosphine) ferrocene]dichloropalladium(II). c Conversion of electrophophile **3** (\%). d \({}^{1}\) isolated yield (%) of compound **5** (_tert_-butyl-3-(2-furyl)-1H-indazole-1-carboxylate), based on compound **3**. No by-products were found with flash chromatography for all entries in this table.  
\end{table}
Table 1: Catalytic Suzuki–Miyaura cross-coupling of compounds **3** with **4**.  
Figure 2: Recycling experiments on Suzuki–Miyaura cross-coupling of compounds **3** with **4** catalyzed by Pd catalyst, immobilized over imidazolium ionic liquid: **(a)** Pd(OAc)\({}_{2}\) over ILs; **(b)** PdCl\({}_{2}\) over ILs; **(c)** PdCl\({}_{2}\)(dppf) over ILs; **(d)** PdCl\({}_{2}\)(dtbpf) over ILs.