18-Crown-6 → (E)-3-Bromo-5-(3-methoxystyryl)pyridine

Participants

Reaction Steps

To a solution of diethyl 3-methoxybenzylphosphonate (5 g, 19.36 mmol) in dimethylformamide (50 mL) at room temperature was added sodium methoxide (2.092 g, 38.7 mmol) and 18-Crown-6 (2.047 g, 7.74 mmol). After stirring at room temperature for 5 min, the reaction was cooled to 0° C. and treated with 5-bromonicotinaldehyde (4.32 g, 23.23 mmol) as a solid in one portion. The ice bath was removed and the reaction stirred at room temperature for 2 h. The reaction was poured into water (500 mL) with vigorous stirring. The resulting suspension was extracted with diethyl ether, washed with water (3×), then brine, dried over magnesium sulfate, and concentrated to an oil which crystallized upon standing. The solid was triturated with a minimum of ethanol (ca. 12 mL) and placed in the freezer for 72 h. The resulting solid was broken up with a spatula, collected by filtration, and rinsed with a minimum of cold ethanol to give 3.79 g (68%) as a white crystalline solid. 1H-NMR (CDCl3, 500 MHz) δ 8.64 (d, J=1.8, 1H), 8.57 (d, J=2.1, 1H), 8.00 (dd, J=2.1, 1.8, 1H), 7.33 (dd, J=7.9, 7.9, 1H), 7.10-7.20 (m, 2H), 7.07 (m, 1H), 7.01 (d, J=16.5, 1H), 6.91 (dd, J=7.6, 2.1, 1H), 3.88 (s, 3H). 13C-NMR (CDCl3, 126 MHz) δ 160.1, 149.5, 146.7, 137.7, 135.1, 134.8, 132.4, 130.0, 123.7, 121.1, 119.6, 114.4, 112.2, 55.4. Mass spec.: 290.14 (MH)+.

Provenance & Evidence