2-Acetylpyridine (Sigma-Aldrich)
Iodine (Fisher Scientific)
Activated charcoal (Sigma-Aldrich)
Dry pyridine - dried by heating to reflux for 3 d under dinitrogen over calcium hydride and degassed before use. Stored in glass ampoules under argon.
Diethyl ether (Fisher Scientific)
Ethanol (Fisher Scientific)
Methanol (Fisher Scientific)

2-Acetylpyridine (6.05 g, 5.6 ml, 50 mmol) was added via syringe to a solution of iodine (12.69 g, 50 mmol) in dry pyridine (50 ml) in a 250 ml round bottomed Schlenk vessel. The round bottomed Schlenk was fitted with a condenser and a N₂ bubbler, and the reaction was stirred and heated at reflux (130^oC) for 2 h. The solution was then cooled to ambient temperature. A 9:1 mixture of diethyl ether/ethanol (20 ml) was added and the solution was cooled to 0^oC using an ice/water bath. The resulting black precipitate was filtered off, washed with a 9:1 mixture of diethyl ether/ethanol (20 ml), and dried in air. The solid was then dissolved in boiling methanol (200 ml) with activated charcoal (20 g) and stirred at reflux for 10 min. The solution was filtered through celite in a fritted funnel and the solvent was removed under reduced pressure to leave the crude product. Recrystallisation from hot methanol (100 ml) resulted in light brown crystals which were filtered, washed with cold methanol (25 ml), and dried in vacuo. Yield = 6.07 g, 18.61 mmol, 37%.

Yield can be increased by reducing the volume of the recrystallisation filtrate and leaving this solution in the fridge.

¹H NMR (400 MHz, 298 K, DMSO) δ_H 9.02 (2H, dd, ³J_HH = 6.5 Hz, ⁴J_HH = 1.0 Hz, Py), 8.87 (1H, dt, ³J_HH = 4.5 Hz, ⁴J_HH = 1.0 Hz, Py), 8.73 (1H, tt, ³J_HH = 8.0 Hz, ⁴J_HH = 1.5 Hz, Py), 8.28 (2H, m, Py), 8.14 (1H, td, ³J_HH = 7.5 Hz, ⁴J_HH = 1.5 Hz, Py), 8.07 (1H, dt, ³J_HH = 8.0 Hz, ⁴J_HH = 1.0 Hz, Py), 7.84 (1H, m, Py), 6.51 (2H, s, CH₂).

¹³C{¹H} NMR (100 MHz, 298 K, DMSO) δ_C 191.49 (C=O), 150.46 (Py), 149.58 (Py), 146.36 (Py), 146.31 (Py), 138.17 (Py), 129.16 (Py), 127.73 (Py), 122.06 (Py), 66.66 (CH₂).

MS (ESI) m/z 199.1 [M+].

Eur. J. Inorg. Chem., 2011, 20, 3050-3058 (supporting information)

¹H NMR spectrum
¹³C NMR spectrum