Menthyl Phenylsulfonyl Acetate

Menthyl phenylsulfonyl acetate was prepared from methyl phenylsulfonyl acetate by solid-liquid PTC trans-esterification conditions without a solvent [1]. To ester 1 (3.21 g, 15 mmol) was added (-)-menthol (3.05 g, 19.5 mmol), potassium carbonate (0.069 g, 3 mmol) and NBu₄HSO₄ (0.034 g, 0.6 mmol). The mixture was heated at 100 °C for 15 h in an oil bath under a dynamic vacuum, cooled to ambient temperature then treated with dilute HCl. The mixture was washed with aqueous NaCl and extracted with ethyl acetate. The product was purified by column chromatography on silica (eluent: pentane/ethyl acetate; 95/5), to give 2 (96%) as a colourless liquid.

¹H NMR (CDCl₃, 200 MHz): 8-7.5 (m, 5H, Ph); 4.7-4.53 (dt, 1H, CH-O); 4.1 (s, 1H, CH₂C=O); 0.95-0.78 (m, 6H, J = 7.2 Hz, 2(CH₃)_b); 0.75-0.62 (d, 3H, J = 7.2 Hz, (CH₃)_a).

¹³C NMR (CDCl₃, 50 MHz): 162 (CO₂); 139, 135, 130 and 129 (C_arom); 78 (CH₂); 61 (CH); 31 (CH₃).

IR: 1740 (CO₂); 1340 and 1130 (SO₂).

MS (IC-NH₃, m/z): 356 (M⁺ + 18, 100%).