Oxalyl chloride → (+/-)-(6-Acetoxy-2,5,7,8-tetramethylchroman-2-yl)acetyl chloride

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Reaction Conditions

Reaction Steps

In a dry flask, a solution of 15.32 g. (50 mmol.) of (±)-(6-acetoxy-2,5,7,8-tetramethylchroman-2-yl)acetic acid in 100 ml. of benzene was heated under N2 to 50°C. as 21.15 ml. (0.25 mol.) of oxalyl chloride was added over 20 minutes. The solution was stirred at 50°C. for another 20 minutes, cooled and stripped of solvent to produce (±)-(6-acetoxy-2,5,7,8-tetramethylchroman-2-yl)acetyl chloride. To a solution of this acid chloride in 200 ml. of dry toluene was added 15 g. of sodium acetate and 1.5 g. of 10% by weight palladium on 90% by weight carbon and 0.30 ml. of quinoline. This mixture was hydrogenated in a Parr apparatus. After 12 hours, the uptake of H2 (about 55 mmole) had virtually ceased. The catalyst was removed by filtration and the filtrates were stripped of solvent. The residue was taken up in ether, washed with 2N aqueous HCl, saturated aqueous sodium bicarbonate solution and saturated brine, dried over sodium sulfate and stripped of solvent to give 15.4 g. of light yellow solid which was chromatographed on 1 kg. of 0.063-0.2 mm silica gel. Elution with 95:5 parts by volume benzene-ethyl acetate gave 11.0 g. of light yellow resin. The material from two such reactions was combined and crystallized from acetone-petroleum ether (b.p. 30°-60°C.) to give (±)-(6-acetoxy-2,5,7,8-tetramethylchroman-2yl)-acetaldehyde as a white powder, sint 66.5°C., m.p. 68°-70°C.

Provenance & Evidence