Trifluoromethanesulfonate

All solutions were prepared using ultrapure water from a Milli-Q water plus system with specific conductivity of less than 0.1 µS cm⁻¹ and the chemicals of analytical grade.
Elastase from porcine pancreas, N-Succinyl-Ala-Ala-Ala-p-nitroanilide, HEPES sodium salt, sodium acetate, sodium hydroxide and acetic acid were purchase to Sigma-Aldrich^® (St. Louis, Missouri, United States). Sodium chloride and dimethyl sulfoxide (DMSO) were purchase to Merck^® (Darmstadt, Germany) and Uvasol^® (Darmstadt, Germany), respectively.
A HEPES buffer solution 0.1 M with sodium chloride (NaCl) 0.5 M at pH 7.5 was used to dissolve the reagents. The buffer solution was prepared weighting 14.6 g of sodium chloride and 12.4g of HEPES and dissolving in about 150 mL of water. The pH 7.5 was adjusted with a 1 M NaOH solution, and final volume was adjusted to 500 mL. A sodium acetate buffer (pH 5.5) solution was used to dissolve the enzyme. The buffer solution was prepared weighting 1.64 g of sodium acetate and dissolving in about 50 mL of water. The pH 5.5 was adjusted with a 17.4 M acetic acid solution, and final volume was adjusted to 100 mL.
All the enzyme elastase porcine was reconstituted by stock solution of 1 U mL⁻¹ using 2.5 mg of powder enzyme in 20 mL of sodium acetate buffer (pH 5.5). The stock solution was divided into 14 eppendorfs with a total volume of 1.43 mL per eppendorf. The eppendorfs were frozen.
A solution of N-Succinyl-Ala-Ala-Ala-p-nitroanilide was prepared daily dissolving 11.25 mg of substrate in 10 mL of DMSO.
For enzyme inhibition assays the aqueous solutions of: 1-Butyl-3-methylimidazolium tetrafluoroborate (bmim [BF₄]), 1-Butyl-3-methylimidazolium chloride (bmim [Cl]), 1-Ethyl-3-methylimidazolium tetrafluoroborate (emim [BF₄]), 1-Ethyl-3-methylimidazolium trifluoromethanesulfonate (emim [TfMs]), 1-Butyl-1-methylpyrrolidinium chloride (bmpyr [Cl]), 1-Butyl-4-methylpyridinium tetrafluoroborate (bmpy (BF₄)), Tetrabutylammonium chloride (tba (Cl)), Tetrabutylammonium acetate (tba (Ac)), Tetrabutylphosphonium methanesulfonate (tbph (ms)), 1-Butyl-3-methylimidazoliumacetate (bmim (Ac)), were prepared daily. ILs were purchased from Sigma-Aldrich^® and kept in anhydrous environment.
The ionic liquids active pharmaceutical ingredients (ILs-APIs) were synthesized according to [35 (link),36 (link)] and the aqueous solutions of lithium bistriflimide, 1-ethyl-3-methylimidazolium salicylate, benzethonium chloride, sodium salicylate, benzalkonium salicylate, trihexyltetradecylphosphonium docusate, benzethonium salicylate, benzethonium docusate, benzethonium bistriflimide, tributylmethylphosphonium salicylate, and trihexyltetradecylphosphonium chloride.
The chemical structures of all ILs and IL-APIs are presented in Supplementary Materials.
The HNE inhibitor named MeOSuc-Ala-Ala-Pro-Val-chloromethylketone was purchased from BioVision^® (San Francisco Bay).

Reagents were purchased and used without purification. Lithium aluminium hydride, reagent grade 95%; pyridinium chlorochromate, 98%; thionyl chloride; silica gel, 200–400 mesh, 60 Å for column chromatography; CDCl3 for NMR spectroscopy; and p-phenetidine, 98%, were supplied by Sigma Aldrich, Germany. Other reagents were provided by Chempur, Poland. TLC sheets Alugram SIL G/UV254 were obtained from Mecherey-Nagel, Germany.
NMR spectra were recorded using a Bruker ARX 300 MHz NMR spectrometer. Chemical shifts (δ in ppm) are given from internal solvent-CDCl3 7.26 ppm for 1H. Abbreviations used in NMR spectra: s—singlet, d—doublet, t—triplet, q—quartet, m—multiplet. IR spectra were recorded with a Thermo Scientific USA Nicolet iS50 FT-IR using the ATR technique. Elemental analyses were performed using a Carlo-Erba NA-1500 elemental analyzer. MS spectra were recorded with a Bruker Daltonic Compact using the ESI technique.
5-[(4-ethoxyanilino)methyl]-N-(4-fluorophenyl)-6-methyl-2-phenylpyrimidin-4-amine (2)
Preparation began with 0.5 g (1.62 mmol) of [4-(4-fluoroanilino)-6-methyl-2-phenylpyrimidin-5-yl]methanol (1), which was placed in a round-bottom flask equipped with a reflux condenser and dissolved in 10 mL of benzene. Then 1 mL of SOCl₂ (1.64 g, 13.78 mmol) was added, and the reaction mixture was left at room temperature for 24 h. After this time, the excess of thionyl chloride and benzene was removed under vacuum, and the solid residue was washed with 2 mL of cold benzene. Next, the crude product was inserted into a round-bottom flask equipped with a magnetic stirrer and a reflux condenser and dissolved in 10 mL of THF. Then 0.69 g (5 mmol) of p-phenetidine was added, and the mixture was left for 48 h at room temperature. After this time, the mixture was poured into 50 mL of cold water and then extracted three times with 10 mL of CHCl₃. The extracts were combined and dried with over 2 g of anhydrous MgSO₄ for 30 min. The drying agent was filtered off, and the solvent was removed under vacuum. The crude product was purified by column chromatography on silica gel using 10% ethyl acetate in CHCl₃ as eluent and crystallized from methanol. The purity of the product was monitored by TLC using chloroform/ethyl ether (3:1) as eluent.
Product characterization: yield 0.43 g, 62%; solid beige; melting point 163–164 °C; ¹HNMR (300 MHz, CDCl₃): δ (ppm) 1.42 (3H, t, CH₃), 2.54 (3H, s, CH₃), 3.60 (1H, broad, NH), 4.01 (2H, q, CH₂), 4.27 (2H, s, CH₂) 6.77–8.41 (13H, m, arom.), 8.77 (1H, s, NH); FT–IR (ATR, selected lines): ν (cm⁻¹) 3295 (N–H); MS (ESI) m/z [M + H]⁺ 429.2036, calculated m/z 429.2085; analysis (%), calc./found: C 72.88/72.95, H 5.88/5.56, N 13.08/12.74.
4-(4-fluoroanilino)-6-methyl-2-phenylpyrimidine-5-carbaldehyde (4)
Prepration began with 0.5 g (1.62 mmol) of [4-(4-fluoroanilino)-6-methyl-2-phenylpyrimidin-5-yl]methanol (1), which was placed in a round-bottom flask equipped with a reflux condenser and dissolved in 10 mL of dichloromethane. Next, the suspension of 0.53 g of PCC (pyridinium chlorochromate; 2.5 mmol) in 10 mL dichloromethane was added. The resulting mixture was stirred at room temperature for 3 h. The reaction mixture was then diluted with 10 mL of diethyl ether, and the solution was decanted. The remaining black resinous polymer was washed with three 5 mL portions of diethyl ether. The extracts were combined, washed with 10 mL of 2% aqueous hydrochloric acid, and two 10 mL portions of water, then dried with over 5 g of MgSO₄, filtered, and concentrated under vacuum. The crude product was purified by column chromatography on silica gel using chloroform as eluent, and then it was crystallized from methanol. The purity of the product was monitored by TLC using chloroform as eluent.
Product characterization: yield 0.34 g, 68%; yellow solid; melting point 184 °C; ¹HNMR (300 MHz, CDCl₃): δ (ppm) 2.86 (3H, s, CH₃), 7.10–8.47 (9H, m, arom.), 10.43 (1H, s, CH), 11.11 (1H, s, NH); FT–IR (ATR, selected lines): ν (cm⁻¹) 3116 (N–H), 1630 (C=O); MS (ESI) m/z [M + H]⁺ 308.1199, calculated m/z 308.1193; analysis (%), calc./found: C 70.35/70.74, H 4.59/4.29, N 13.67/13.36.
5-[(4-ethoxyphenyl)imino]methyl-N-(4-fluorophenyl)-6-methyl-2-phenylpyrimidin-4-amine (3)
Method A
The amount of 0.3 g of 4-(4-fluoroanilino)-6-methyl-2-phenylpyrimidine-5-carbaldehyde (3) (0.98 mmol) was placed in a round-bottom flask equipped with a reflux condenser and dissolved in 10 mL of THF. Then 0.2 g of p-phenetidine (1.5 mmol) was added. The reaction mixture was refluxed for 6 h, then it was cooled down and poured into 25 mL of 2% aqueous hydrochloric acid. The solution was extracted three times with 10 mL of CHCl₃. The extracts were combined and dried with over 2 g of anhydrous MgSO₄ for 30 min. The drying agent was filtered off, and the solvent was removed under vacuum. The crude product was purified by column chromatography on silica gel using CHCl₃ as eluent. The purity of the product was monitored by TLC using chloroform as eluent.
Yield: 0.28 g; 66%; yellow solid; melting point: 187–188 °C;; ¹HNMR (300 MHz, CDCl₃): δ (ppm) 1.46 (3H, t, CH₃), 2.81 (3H, s, CH₃), 4.09 (2H, q, CH₂), 6.97–8.50 (13H, m, arom.), 8.96 (1H, s, CH), 12.75 (1H, s, NH); FT–IR (ATR, selected lines): ν (cm⁻¹) 1642 (C=N); MS (ESI) m/z [M + H]⁺ 427.1882, calculated m/z 427.1929; analysis (%), calc./found: C 73.22/73.50, H 5.44/5.16, N 13.14/13.19.
Method B
The amount of 0.3 g of 4-(4-fluoroanilino)-6-methyl-2-phenylpyrimidine-5-carbaldehyde (3) (0.98 mmol) was placed in a round-bottom flask equipped with a reflux condenser and dissolved in 10 mL of THF. Then 0.2 g of p-phenetidine (1.5 mmol) and 2 mg of indium(III) trifluoromethanesulfonate were added. The reaction mixture was stirred at room temperature for 48 h and processed as in Method A. Yield: 0.40 g; 94%.
Method C
The amount of 0.3 g of 4-(4-fluoroanilino)-6-methyl-2-phenylpyrimidine-5-carbaldehyde (3) (0.98 mmol) was placed in a round-bottom flask equipped with a reflux condenser and suspended in 10 mL of methanol. Then 0.2 g of p-phenetidine (1.5 mmol) and 2 mg of indium(III) trifluoromethanesulfonate were added. The reaction mixture was stirred at room temperature for 48 h and processed as in Method A. Yield: 0.15 g; 28%.

Potassium trifluoromethanesulfonate and 1,10-phenanthroline
monohydrate were acquired from Sigma-Aldrich (Merk, Spain) and ruthenium
trichloride trihydrate (RuCl₃·3H₂O) from
Johnson Matthey. Deuterated solvents were obtained from Eurisotop,
except for deuterated trifluoroacetic acid, which was obtained from
Sigma-Aldrich. All chemicals were used as received without further
purification.

Solvents were purchased from Millipore Sigma and used as received unless otherwise noted. All aqueous solutions were prepared with deionized water. Deuterated solvents were purchased from Cambridge Isotopes Laboratories, Inc. Cambridge Isotope Laboratories, Inc. and used as received. 3,5-dibromobenzoic acid, ethyl-3,5,-dibromoisonicotinate, and poly(ethylene glycol) were purchased from Milipore Sigma. 3-Ethynylpyridine was purchased from AmBeed Inc. Tetrakis(acetonitrile)palladium(II) bis(trifluoromethanesulfonate) was purchased from TCI America.