[CH:1]([N-]C(C)C)([CH3:3])[CH3:2].[Li+].C([O:12][C:13](=[O:24])[CH2:14][O:15][C:16]1[CH:21]=[CH:20][C:19]([Cl:22])=[C:18]([Cl:23])[CH:17]=1)C=C.Cl[Si](C)(C)C.[OH-].[Na+].ClC1C=C(C=CC=1Cl)OCC(O)=O>O1CCCC1.C(N(CC)CC)C>[Cl:23][C:18]1[CH:17]=[C:16]([CH:21]=[CH:20][C:19]=1[Cl:22])[O:15][CH:14]([CH2:3][CH:1]=[CH2:2])[C:13]([OH:12])=[O:24]To a stirred solution of anhydrous tetrahydrofuran (100 cm3) cooled to −100° C. in an ethyl ether/liquid nitrogen bath under an atmosphere of dry nitrogen was added a 2M solution of lithium diisopropylamide (6.30 cm3, 12.7 mmol) in tetrahydrofuran followed by dropwise addition at −100° C. of a solution of (3,4-dichloro-phenoxy)-acetic acid allyl ester (3.00 g, 11.5 mmol) in anhydrous tetrahydrofuran (15 cm3) over 5 minutes. The solution was stirred at −100° C. for 1 hour and the supernatant (3.30 cm3, 11.8 mmol) of a centrifuged 1:1 mixture of chlortrimethylsilane and triethylamine was added dropwise over 5 minutes at −100° C. The solution was stirred an additional 1 hour at −100° C. and allowed to warm to ambient temperature. To the solution was added 1 N sodium hydroxide (250 cm3) and the mixture stirred 10 minutes at ambient temperature. The aqueous layer was separated, extracted with ethyl ether (2×50 cm3) and acidified with 1 N HCl to pH 1.0. The acidified aqueous was extracted with ethyl ether (3×50 cm3), the combined ethyl ether extracts washed with brine (50 cm3), dried over magnesium sulfate, vacuum filtered and the filtrate volatile fractions removed in vacuo to afford a 4:1 mixture of the title compound and (3,4-dichloro-phenoxy)-acetic acid as a pale yellow solid (1.12 g, 37.3%) with negative ESI (M−H)−260.1.
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