Yield:928772-51-4 97%

Reaction Conditions:

Stage #1: 3,4-dihydro-2H-quinoline-1,7-dicarboxylic acid 1-tert-butyl ester 7-methyl esterwith methanol;sodium hydroxide;water at 20; for 5 h;
Stage #2: with hydrogenchloride;water

Steps:

57.3

Step 3: A solution of crude 3,4-dihydro-2H-quinoline-1,7-dicarboxylic acid 1-tert-butyl ester 7-methyl ester (2.7 g, 9.2 mmol) in methanol (30 ml) was treated with 3N NaOH (10 ml, 30 mmol, 3.3 equiv.) and stirred at room temperature for 5 h. The methanol was evaporated and the residual slurry was treated with 3N HCl (10 ml). The white precipitate was filtered, washing with water, and dried under high vacuum to afford 3,4-dihydro-2H-quinoline-1,7-dicarboxylic acid 1-tert-butyl ester as a white solid, 2.5 g (97%). MS (ISP): m/e=276.1 (M-H); δ_H (300 MHz; CDCl₃) 8.40 (0.25H, s), 8.33 (0.75H, s), 7.70 (0.25H, d), 7.64 (0.75H, d), 7.14 (1H, m), 3.75 (2H, m), 2.82 (2H, m), 1.94 (2H, m), 1.54 (9H, s).

References:

US2007/60567,2007,A1 Location in patent:Page/Page column 30