Water → 2,2,5,5-Tetramethyltetrahydro-3-ketofuran

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Mercuric oxide (600 mg) was dissolved in 200 mL of water containing 2 mL of concentrated H2SO4. Solid 2,5-dimethyl-3-hexyne-2,5-diol (50.0 g, 352 mmol) was added and the solution was heated until the homogeneous solution turned cloudy. Heating was stopped and the flask was stirred in a room temperature water bath for 30 min. The solution was distilled and 250 mL of distillate was collected (more H2O was added). The biphasic material was taken up into ether, separated, washed with brine, dried over MgSO , filtered, evaporated and distilled (~150° C.) to give 44.5 g (89%) of dihydro-2,2,5,5-tetramethyl-3(2H)-furanone as a water-white oil. Dihydro-2,2,5,5-tetramethyl-3(2H)furanone (32.1 g, 226 mmol) in 50 mL of ether was added dropwise to a suspension of sodium hydride (18.1 g of 60%, 453 mmol) in 400 mL of ether containing two drops of ethanol and 36.5 mL (453 mmol) of ethyl formate stirred at 0° C. After stirring overnight at room temperature, the reaction mixture was taken up into water, washed with additional ether, acidified with 6N HCl and extracted into ether. The combined ether layers were washed with water and brine, dried over MgSO4, decolorized with charcoal, filtered through celite and evaporated. The solid residue was recrystallized from a small volume of ether and a large quantity of hexanes. The solid was isolated by filtration and dried to give 30.4 g (79%) of 4-hydroxymethylene-dihydro-2,2,5,5-tetramethyl-3(2H)-furanone as an off-white solid. Ethylenediamine (1.15 mL, 17.4 mmol) was added to a solution of 4-hydroxymethylene-dihydro-2,2,5,5-tetramethyl-3(2H)furanone (5.9 g, 34.7 mmol) in 40 mL of THF. This solution was refluxed for one hour. The solvents were evaporated under high vacuum with moderate heating. The solid residue was slurried in 50 mL of cold ether and filtered to give 5.3 g (76%) of off-white solid. Recrystallization from 50 mL of THF followed by drying at 70° C. (1 Torr) for 6 hours gave 4.0 g of 1,2-bis[dihydro-2,2,5,5-tetramethy13(2H)furanone-4-methyleneamino]ethane as a white solid: Anal. Calc'd for C20H32N2O4 : C, 65.93; H, 8.79; N, 7.69. Found: C, 65.68; H, 8.90; N, 7.65.

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