Sulfuric Acid → (2R)-4-methoxycarbonyl-2-methyltetrahydrofuran-3-one

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A solution of methyl (R)-(+)-lactate (30 g) in diethyl ether (60 ml) was added dropwise to a stirred mixture of sodium hydride (65%, 10.42 g) and diethyl ether (180 ml) which had been cooled to -35° C. The mixture was allowed to warm to 0° C. and stirred for 20 minutes. The mixture was evaporated. To the residue so obtained there was added a solution of methyl acrylate (29.2 ml) in DMSO (120 ml) which had been cooled to 10° C. The mixture was stirred in an ice-bath for 30 minutes and at ambient temperature for 2 hours. The mixture was poured into cold dilute (5%) aqueous sulphuric acid and extracted with diethyl ether. The organic phase was washed with a cold aqueous sodium bicarbonate solution and with brine, dried (MgSO4) and evaporated. The residue was distilled to give (2R)-4-methoxycarbonyl-2-methyltetrahydrofuran-3-one (16.5 g, 37%), b.p. 66°-68° C. (0.5 mm Hg), [alpha]20 =+55.3° (conc.=1.16 g per 100 ml of chloroform).

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