[CH3:1][C:2]([C:7]1[CH:12]=[CH:11][CH:10]=[CH:9][CH:8]=1)([CH3:6])[C:3](O)=[O:4].S(Cl)(Cl)=O.C(=O)([O-])[O-].[K+].[K+].[CH3:23][N:24](Cl)[CH3:25].Cl>C1(C)C=CC=CC=1.O.C(OC)(C)(C)C>[CH3:23][N:24]([CH3:25])[C:3](=[O:4])[C:2]([CH3:6])([C:7]1[CH:12]=[CH:11][CH:10]=[CH:9][CH:8]=1)[CH3:1]Dissolve 2-methyl-2-phenyl-propionic acid (15.08, 91.2 mmol) in toluene (80 mL) and add, by dropwise addition over 5 minutes, thionyl chloride (15 mL, 206 mmol). Stir at room temperature overnight, add additional thionyl chloride (3 mL, 41.1 mmol) and heat to reflux for 1 hour. Remove excess thionyl chloride by azeotropic distillation with toluene (40 mL). Add toluene (20 mL) to the reaction mixture along with a solution of potassium carbonate (28.0 g, 203 mmol) in water (40 mL). Add, by dropwise addition, a 40% aqueous solution of dimethylamino hydrochloride (20 mL, 0.18 mol) without cooling and stir for 2 hours. Add tert-butylmethyl ether (75 mL) following by slow addition of aqueous HCl (2N, 75 mL) with vigorous stirring. Separate the organic layer and wash with aqueous HCl (2N, 75 mL), saturated sodium hydrogen carbonate (25 mL) and brine (50 mL). Dry the organic layer over (Na2SO4), filter, evaporate the filtrate in vacuo and purify by crystallization to give 2-methyl-2-phenyl-propionic acid, dimethylamide (15.35 g, 88%) as a white solid; mp 57-59° C.
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