A
1-L, three-necked, round-bottomed flask with
mechanical stirrer and
vacuum outlet (Note
1) is charged with powdered
cerium (III) chloride (CeCl3 · 7H2O, 52.92 g, 0.142 mol) (Note
2). The flask is immersed to the necks in an
oil bath and evacuated to 0.2 mm. The solid is agitated by stirring as the flask is heated to 150°C for 2 hr. After the flask is cooled to room temperature, it is vented to the atmosphere and quickly purged with a stream of dry
nitrogen for 2 min. At this stage, the flask is fitted with a
low-temperature thermometer and a
graduated 250-mL addition funnel containing
300 mL of dry tetrahydrofuran (THF) (Note
3), and capped with a
rubber septum. Connection to a
dry nitrogen line with a
pressure relief bubbler is made via a needle through the septum.
Tetrahydrofuran is run into the flask with good stirring, so that an even suspension results (Note
4). The white suspension is stirred at room temperature for 2 hr. Meanwhile, the addition funnel is charged with
trimethylsilylmethylmagnesium chloride (Me3SiCH2MgCl, 1 M solution in ethyl ether, 142 mL, 0.142 mol) (Note
5) and (Note
6), transferred via stainless-steel cannula. The contents of the flask are cooled to −65°C with a
dry ice/2-propanol bath, and the Grignard solution is added dropwise over a period of 40–50 min, so that the temperature of the reaction mixture remains below −60°C. The addition funnel is removed from the setup, with the septum/nitrogen inlet connected directly to the flask. After the cold mixture is stirred for 15 min more,
ethyl cinnamate (10.32 g, 0.0586 mol) (Note
7) is added via syringe over a 2–3-min period. Stirring is continued as the flask is allowed to warm slowly to room temperature (Note
8). The off-white to beige reaction mixture is cooled to <5°C (
ice-water bath) and quenched by the portionwise addition of chilled
1 M hydrochloric acid (200 mL), so that the internal temperature remains below 20°C (Note
9). The layers are separated, and the aqueous phase is extracted twice with
ethyl ether (100 mL each). The combined organic layers are washed with saturated
sodium bicarbonate solution (Note
10) and dried over
sodium sulfate, and the solvents are removed at a
rotary evaporator (25°C at 60 mm). The residual oil is transferred to a
100-mL, round-bottomed flask and distilled bulb-to-bulb (Note
11). The product (
9.69–9.85 g,
76.5–78%) (Note
12) is collected at an air-bath temperature of 110–112°C, 0.20 mm.