A solution of 3-(6-(methoxycarbonyl)-3,3-dimethyl-1,2,3,4-tetrahydroquinolin-2-yl)-benzoic acid (150 mg, 0.44 mmol, 1.0 eq.) and 1,1′-carbonyldiimidazole (214 mg, 1.32 mmol, 3.0 eq.) in tetrahydrofuran (3 mL) was heated to 60° C. for 2 h, then was cooled to room temperature and treated with benzenesulfonamide (89.6 mg, 0.57 mmol, 1.3 eq.). After stirring for 10 min, the reaction mixture was treated with dropwise addition of a solution of 1,8-diazabicyclo[5.4.0]undec-7-ene (221 mg, 1.45 mmol, 3.3 eq.) in tetrahydrofuran (1 mL). Upon completion of addition, the resultant mixture was stirred overnight. Thin layer chromatography (petroleum ether:ethyl acetate=1:1) showed the reaction was complete. The reaction mixture was quenched with brine and acidified with 1N hydrochloric acid solution to pH=6, extracted with ethyl acetate (twice). The combined organic layers were washed with brine for 3 times, dried over anhydrous magnesium sulfate. Removal of the solvent in vacuo gave 252 mg of methyl 3,3-dimethyl-2-(3-(phenylsulfonylcarbamoyl)phenyl)-1,2,3,4-tetrahydroquinoline-6-carboxylate as a white solid, which was pure enough for next step without further purification. MS (ESI+APCI) M+1=479.2.
