Dichloro(N,N,N',N'-tetramethylethylenediamine)zinc(II)

Typical Procedure:To a stirred, cooled (-78 °C) solution of 3,4-ethylenedioxythiophene (426 mg, 3.0 mmol) in dry THF (5 mL) is slowly added n-BuLi (1.6 M hexanes solution, 3.0 mmol). The temperature is slowly raised to 0 °C before introduction ZnCl₂·TMEDA (757 mg, 3.0 mmol). The mixture is stirred for 1 h at 0 °C and PdCl₂ (11 mg, 2 mol%), dppf (33 mg, 2 mol%), 2,6-dichloropyridine (444 mg, 3.0 mmol) are successively added. The reaction mixture is stirred for 48 h at 60 °C, quenched with water (1 mL) and filtered over celite^®. After addition of an aqueous saturated solution of NaCl (10 mL), the mixture is extracted with CH₂Cl₂ (3 x 10 mL). The combined organic layers are dried over MgSO₄, filtered and concentrated under reduced pressure. Purification by flash chromatography on silica gel (heptane/CH₂Cl₂: 6/4) and crystallization in dichloromethane gives 2-chloro-6-(3,4-ethylenedioxy-2-thienyl)pyridine (569 mg, 75%) as yellow crystals.