[Cl:1][C:2]1[CH:3]=[C:4]([O:9][CH3:10])[CH:5]=[CH:6][C:7]=1[Cl:8].C([Li])CCC.CN(C)[CH:18]=[O:19]>O1CCCC1.CCCCCC.ClCCl>[Cl:1][C:2]1[C:7]([Cl:8])=[CH:6][CH:5]=[C:4]([O:9][CH3:10])[C:3]=1[CH:18]=[O:19]
3,4-Dichloroanisole (12.5 g, 70.6 mmol) was dissolved in tetrahydrofuran (130 ml) and cooled to −76° C. n-Butyllithium (31 ml of 2.5 molar in hexanes, 77.7 mmol) was added dropwise keeping the temperature below −70° C. The solution was stirred at −70° C. for 30 minutes, then dimethylformamide (6.0 ml, 77.7 mmol) was added dropwise. The mixture was allowed to warm up to room temperature and was then poured onto ice (500 ml) and extracted with diethyl ether. The ether extracts were washed with brine then dried over anhydrous Na2SO4, filtered, and the solvent removed in vacuo to give the crude product. This material was stirred and heated to just below the reflux temperature in hexane (100 ml) and dichloromethane (5 ml), then cooled, and the solid filtered off to give the title compound as an off-white powder (10.0 g).
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