General experimental for nuclear-chemical synthesis: All ion–molecular reactions were carried out in sealed glass ampoules containing the source of the phenyl cations (tritiated benzene), the nucleophile of interest (4-picoline) and filled with an inorganic salt to serve as a stabilizing anion (KBF4). The molar ratio for benzene and substrate was about 1:1000 (1 μL of hexane solution of tritium double-labeled benzene 4 Cu/sm3 and 5.3 μL of the picoline). The ampoules were sealed cold and kept at 0–5°C during accumulation time (about 1 month). After this period, the radioactivity of the obtained products is enough for the detection. The ampoules were opened, solvent added (acetone), and the mixture subjected to TLC analysis on glass plates (Reverse phase C18 silica, fluorescent indicator, CH3CN). Radioactivity of the sorbent layer was measured using a scintillation spectrometer RackBeta 1215 (LKB Wallac, Finland).
General procedure for the synthesis of 2(or 3)-phenyl-4-picoline
A 20-mL Schlenk tube was charged with 2(or 3)-bromo-4-methylpyridine (0.172 g, 1 mmol), phenylboronic acid (0.146 g, 1.2 mmol), K2CO3 (0.276 g, 2 mmol), dioxane (7 mL), water (3 mL), and PdCl2(PPh3)2 (0.0071 g, 0.01 mmol, 1 mol% of Pd) under argon. The reaction mixture was placed in a pre-heated oil bath at 150°C and stirred under reflux for 1 h. After this time, the reaction mixture was diluted with 20-mL H2O and extracted with Et2O (2 × 10 mL). The combined organic layers were washed with 5% KOH (2 × 5 mL), H2O (2 × 5 mL), brine (2 × 5 mL), dried over Na2SO4 and filtrated through a pad of silica gel. The solvent was removed by evaporation in vacuum.
A pale yellow oil was obtained. Yield: 0.156 g (92%). 1H NMR (acetone-d6, 400 MHz): 2.39 (s, 3H), 7.12 (d, J = 4.80 Hz, 1H), 7.40 (t, 1H), 7,46 (t, 2H), 7.74 (s, 1H), 8.11 (d, J = 8.08 Hz, 2H), 8.50 (d, J = 4.80 Hz, 1H); Anal. Calcd for C12H11N: C, 85.17; H, 6.55; N, 8.28. Found: C, 85.21; H, 6.62; N, 8.17.
A pale yellow oil was obtained. Yield: 0.162 g (96%). 1H NMR (acetone-d6, 400 MHz): 2.26 (s, 3H), 7.25 (d, J = 4.55 Hz, 1H), 7.37 (d, 2H), 7,40 (t, 1H), 7.47 (t, 2H), 8.37 (s, 1H), 8.41 (d, J = 4.80 Hz, 1H); Anal. Calcd for C12H11N: C, 85.17; H, 6.55; N, 8.28. Found: C, 85.26; H, 6.48; N, 8.26.