Chloroacetone → 1-(4-(Benzyloxy)benzofuran-2-yl)ethanone

Participants

Reaction Conditions

Reaction Steps

A solution of 2-(benzyloxy)-6-hydroxybenzaldehyde (Example 38B, 11.10 g, 48.63 mmole) in N,N-dimethylformamide (120 mL) was treated with powdered anhydrous cesium carbonate (15.8 g, 48.63 mmol) added all at once. The resulting mixture was stirred in vacuo for 10 min and then flushed with nitrogen. The reaction flask was placed in a water bath (22° C.) and treated with chloroacetone (4.65 mL, 58.4 mmol) added dropwise over 10 min. The resulting mixture was then stirred at 22° C. for 18 h (no starting aldehyde left by tlc and formation of the intermediate alkylated aldehyde). The reaction mixture was then maintained under vacuum (10 mbar) for 15 min to remove any un-reacted chloroacetone and then flushed with nitrogen. Then anhydrous cesium carbonate (1.0 g, 3.1 mmol) was added and the mixture was heated at 55° C. and stirred for 40 h (more cesium carbonate, 1 g, was added after 24 h and 32 h) till complete conversion of the intermediate alkylated aldehyde into the benzofuran as monitored by TLC. The solid was filtered and washed with N,N-dimethylformamide. The filtrate was evaporated in vacuo and the residual oil was diluted with ethyl acetate (400 mL), washed with cold 0.1 N hydrochloric acid, saturated sodium bicarbonate and brine. After drying over anhydrous magnesium sulfate, evaporation of the solvent gave a thick syrup. Chromatography on silica gel (4.5×12 cm, elution toluene-ethyl acetate 2-4%) gave 11.67 g (90% yield) of the title benzofuran as a light yellow solid. Recrystallization from a mixture of ethyl acetate (40 mL) and hexane (40 mL) gave colorless prisms (10.50 g). LC (Method A): 2.162 min. HRMS (ESI) calcd for C17H15O3 [M+H]+ m/z 267.1016, found 267.1022. 1H NMR (CDCl3, 600 MHz) δ ppm: 2.56 (s, 3H), 5.20 (s, 2H), 6.73 (d, J=8.0 Hz, 1H), 7.17 (d, J=8.4 Hz, 1H), 7.3-7.5 (m, 6H), 7.63 (s, 1H).

Provenance & Evidence