An
oven-dried, three-necked, 1-L, round-bottomed Morton flask equipped with a mechanical stirrer, gas bubbler outlet, 125-mL, pressure-equalizing addition funnel fitted with a rubber septum, and a nitrogen inlet (Note
1) is charged with
11.2 g (110 mmol) of phenylacetylene (Note
2) and
60 mL of dry tetrahydrofuran (THF) (Note
3). The addition funnel is charged with
60 mL of 2 M isopropylmagnesium chloride (Note
4) which is then added over a 5-min period (Note
5). The addition funnel is rinsed with
10 mL of dry THF and the solution is stirred at room temperature for 1 hr. The addition funnel is charged with
72 mL of 1 M anhydrous zinc bromide in THF (Note
6) which is then added to the light-grey solution over a 5-min period (Note
7). The addition funnel is rinsed with
10 mL of dry THF, and the mixture is stirred for a further 30 min at room temperature (Note
8). The addition funnel is charged with a solution of
22.6 g (100 mmol) of 2-(phenylsulfonyl)tetrahydro-2H-pyran (Note
2) dissolved in
100 mL of dry THF, which is then added over a 5-min period (Note
9). The resulting grey solution is stirred at room temperature for 18 hr and then quenched with
300 mL of 1 M hydrochloric acid (Note
10). The mixture is transferred to a
single necked, 1-L, round-bottomed flask and concentrated under reduced pressure (40°C, 100 mm) to remove the THF. The residue is transferred to a
1-L separatory funnel and extracted with
300 mL of isopropyl acetate (i-PrOAc). The extract is sequentially washed with water
(150 mL), 1 M aqueous dibasic potassium phosphate (3 × 150 mL), and
brine (150 mL). The extract is dried over
anhydrous sodium sulfate, filtered through a
sintered glass funnel, washing the residue with more i-PrOAc, and then concentrated under reduced pressure (40°C, 10 mm) to give
19.6 g of crude product as a pale yellow liquid (Note
11). This is distilled under reduced pressure to afford
18.3 g (
98%) of
tetrahydro-2-(phenylethynyl)-2H-pyran as a colorless liquid, bp
110–115°C (0.01 mm) (Note
12).