P(Cl)(Cl)(Cl)(Cl)[Cl:2].[CH3:7][C:8]([CH3:16])([C:13](=O)[CH3:14])[C:9]([O:11][CH3:12])=[O:10]>C(Cl)Cl.CN(C=O)C>[Cl:2][C:13](=[CH2:14])[C:8]([CH3:16])([CH3:7])[C:9]([O:11][CH3:12])=[O:10]To a suspension of PCl5 (270 g, 1.3 mol) in CH2Cl2 (1000 mL) was added dropwise methyl 2,2-dimethyl-3-oxobutanoate (85 g) at 0° C., following by addition of approximately 30 drops of dry DMF. The mixture was heated at reflux overnight. The reaction mixture was cooled to ambient temperature and slowly poured into ice water. The organic layer was separated and the aqueous phase was extracted with CH2Cl2 (500 mL×3). The combined organic layers were washed with saturated aqueous NaHCO3 and dried over anhydrous Na2SO4. The solvent was evaporated and the residue was distilled under reduced pressure to give methyl 3-chloro-2,2-dimethylbut-3-enoate (37 g, 23%). 1H NMR (400 MHz, CDCl3) δ 5.33 (s, 1H), 3.73 (s, 3H), 1.44 (s, 6H).
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