[CH3:1][C:2]1([CH3:8])[C:6](=[O:7])[CH2:5][CH2:4][O:3]1.[H-].[Na+].[CH2:11]([OH:13])C.C(OCC)=O>CCOCC.O>[OH:13][CH:11]=[C:5]1[CH2:4][O:3][C:2]([CH3:8])([CH3:1])[C:6]1=[O:7]An ether solution of dihydro-2,2-dimethyl-3(2H)-furanone (4.55 g, 39.9 mmol) in 30 mL of ether was added dropwise to a suspension of sodium hydride (3.2 g of 60%, 80 mmol) in 150 mL of ether containing three drops of ethanol and 6.5 mL (80 mmol) of ethyl formate stirred at 0° C. After stirring overnight at room temperature, the reaction mixture was taken up into water, the ether layer separated, washed with additional ether, acidified with 6N HCl and with water and brine, dried over MgSO4, decolorized with charcoal, filtered and evaporated to leave 2.4 g of 4-hydroxymethylene-dihydro-2,2-dimethyl-3(2H)furanone as a colorless oil (43%).
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