p-Toluenesulfonic acid → Cyclohexanecarboxylic acid, 1-methylethyl ester

Participants

Reaction Conditions

Reaction Steps

To a solution of cyclohexanecarboxylic acid (22.0 g, 172 mmol) in isopropanol (66 mL) and cyclohexane (44 mL) p-TsOH (653 mg, 3.43 mmol) was added. The mixture was heated with stirring to 70-73° C. and solvent was slowly distilled off whereas the volume was kept relatively constant by addition of fresh solvent mixture. After 6 h, a second portion of p-TsOH (653 mg, 3.43 mmol) was added and the reaction mixture was stirred at 71° C. overnight (without distilling off solvent). After a total of 24 h, the cooled reaction mixture was concentrated to ¼ volume. Ice and saturated aq. NaHCO3 were added and the mixture was extracted twice with TBME. The organic phases were washed to neutral with diluted aq. NaCl solution, combined, dried over sodium sulfate and concentrated. The crude product (28.5 g) was distilled at 40° C. (0.2-0.16 mbar) to afford 27.75 g (93%) cyclohexanecarboxylic acid isopropyl ester as a colorless liquid, GC purity 98% (area). 1H-NMR (CDCl3, 400 MHz): ppm 1.21 (d, 6H), 1.17-1.34 (m, 3H), 1.35-1.49 (m, 2H), 1.55-1.80 (m, 3H), 1.82-1.92 (m, 2H), 2.20-2.29 (m, 1H), 4.94-5.04 (m, 1H).

Provenance & Evidence