Acetic Anhydride → 1-(2,3-Dihydro-5-benzofuranyl)ethanone

To a stirred solution of 12 g [100 mmole) 2,3-dihydrobenzofuran in 80 ml carbon disulfide was added in portions 30 g (225 mmole) anhydrous aluminum chloride. The mixture was heated at reflux and 18.9 ml (200 mmole) acetic anhydride was slowly added. Refluxing was continued for one hour after the addition was completed. Carbon disulfide was then removed by distillation and the residue was cooled in ice. Cracked ice (100 ml) was slowly added, the reaction mixture was acidified to pH 1 and diluted with water (100 ml) and extracted with ethyl ether (2×250 ml). The extracts were dried (Na2SO4) .and the ether evaporated. The residual oil was purified pn a column of silica gel (600 ml), eluting with 9:1 (v/v) hexane/ethyl acetate, then with a 4:1 (v/v) mixture of the same solvents, and finally with a 2:1 mixture. The product fractions were combined and evaporated to obtain the desired product as an oil; 1H-NMR(CDCl3)ppm(delta): 2.4 (s, 3H), 3.2 (t, 2H), 4.6 (t, 2H), 6.7 (d, 1H), 7.7 (m, 2H).