C.
7,7-Dimethoxybicyclo[2.2.1]heptene. A 3-l. three-necked flask is equipped with a
sealed Hershberg stirrer,
2 a condenser fitted with a
nitrogen inlet to maintain a slight positive pressure, and a
pressure-equalizing dropping funnel. The flask is placed in a heating mantle, and into it are placed
1.5 l. of tetrahydrofuran,
130 g. (5.7 g. atoms) of sodium chopped into 5-mm. cubes, and
190 ml. (150 g., 2.0 moles) of t-butyl alcohol. This mixture is stirred vigorously and brought to gentle reflux (Note
12). As soon as refluxing occurs,
106 g. (0.36 mole) of 7,7-dimethoxy-1,2,3,4-tetrachlorobicyclo[2.2.1]hept-2-ene is added dropwise over a 2-hour period (Note
13). The mixture is heated under reflux for 38 hours, cooled to room temperature, and filtered through a wire screen to remove the unreacted
sodium. The dark filtrate is refiltered by suction through Celite in a
Buchner funnel (Note
14). The filtrate is mixed with 2 l. of chopped ice and
500 ml. of ether. The aqueous phase is separated (Note
15), and the organic phase is washed with
500-ml. portions of saturated aqueous sodium chloride until the washings are clear. The ethereal solution is dried over anhydrous
magnesium sulfate and concentrated to a dark oil by removal of the
ether by fractional distillation. The oil is fractionally distilled through a
6-in. Vigreux column to yield
17–24 g. (
31–43%) of colorless liquid, b.p.
58–68° (17 mm.),
n25D 1.4598 (Note
16) and (Note
17).