[Cl:1][C:2]1[C:3]([CH3:8])=[N:4][O:5][C:6]=1[CH3:7].NCCCCN.C([Li])CCC.[C:20](=[O:22])=[O:21]>CCCCCC.C(OCC)C.O.C1COCC1>[CH3:8][C:3]1[C:2]([Cl:1])=[C:6]([CH2:7][C:20]([OH:22])=[O:21])[O:5][N:4]=1
A mixture of 12 g of 4-chloro-3,5-dimethyl isoxazole (prepared by chlorination of 3,5-dimethyl-isoxazole in acetic acid at 50° C) in freshly distilled THF and 13.8 ml of tetramethylenediamine in a 3-necked vessel was reacted under a nitrogen atmosphere with 50 ml of a 20% n-butyl lithium solution in hexane at -70° C and the mixture was stirred for 2 hours. A stream of carbon dioxide was passed therethrough for an hour and then water and diethyl ether were added thereto. The aqueous layer was extracted with diethyl ether at a pH of 2 and the combined organic layers were dried over magnesium sulfate, treated with activated carbon and concentrated to dryness under reduced pressure. The 6.3 g of product was crystallized from a petroleum ether-acetone mixture to obtain 3-methyl-4-chloro-isoxazole-5-yl acetic acid melting at 128°-131° C (sublimation)
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