Potassium Carbonate → Methyl 5-chloro-2-ethynylbenzoate

To a solution of methyl 5-chloro-2-[2-(trimethylsilyl)ethynyl]benzoate (10 g, 37.5 mmol) in Methanol (150 ml) was added K2CO3 (10.36 g, 75 mmol) at room temperature and in air. The reaction mixture was stirred for 1 hour before being concentrated under reduced pressure. The residue was dissolved in deionized water (50 ml) and EtOAc (50 ml). The phases were separated and the aqueous layer was extracted with EtOAc (2×50 ml). The combined organic extracts were dried over MgSO4, filtered and concentrated under reduced pressure. The residue was purified by FCC (50 g silica, Isolute cartridge, gradient of eluents; 95:5 Heptane:EtOAc to 9:1 Heptane:EtOAc) to give 5.75 g (55.2%) of methyl 5-chloro-2-ethynylbenzoate as an orange oil that solidified upon standing. This material contained 30% of ethyl ester which was suitable for use without any further purification. LC-MS 38%, 1.98 min (3 minute LC-MS method), m/z=195.0/196.9, 1H NMR (500 MHz, Chloroform-d) δ ppm 7.93 (d, J=2.2 Hz, 1H), 7.55 (d, J=8.3 Hz, 1H), 7.45 (dd, J=8.3, 2.3 Hz, 1H), 3.94 (s, 3H), 3.43 (s, 1H).