Triethylamine → 4-Hydroxybicyclo[3.2.1]oct-3-en-2-one triethylammonium salt

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Reaction Steps

1.38 g (0.01 mol) of 4-methylene-3-oxabicyclo[3.2.1]octan-2-one are stirred for 12 hours at a temperature of 20° C. in the presence of 1.11 g (0.01 mol) of triethylamine and 65 mg (1 mmol) of potassium cyanide in 20 ml of acetonitrile, the 4-hydroxybicyclo[3.2.1]oct-3-en-2-one triethylammonium salt formed partially crystallising out. While controlling the temperature, 2.64 g (0.01 mol) of freshly prepared 4-methanesulfonyl-2-nitrobenzoyl chloride are introduced into the resulting suspension at a temperature of 20° C. After stirring for 30 minutes at a temperature of 20° C., extraction is carried out with ethyl acetate against 5% sodium hydrogen carbonate solution, followed by washing once with dilute hydrochloric acid and once with water and evaporating to dryness. The residue (3.2 g) is filtered through a small amount of silica gel (eluant: ethyl acetate/hexane 1:1), yielding 4-methanesulfonyl-2-nitrobenzoic acid 4-oxobicyclo[3.2.1]oct-2-en-2-yl ester in form of a viscous oil: yield: 2.48 g 67.9%); 1H-NMR (CDCl3): 8.84 ppm, s, 1H, 8.34 ppm, d, 1H, 8.03 ppm, d, 1H, 5.90 ppm, s, 1H, 3.17 ppm, s, 3H, 3.0–3.15 ppm, 2H, 1.6–2.3 ppm, 6H.

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