Methanesulfonic Acid → Isatin

Participants

Reaction Steps

Intermediate 3 (20 g, 0.1 mol) was added in small portions, with stirring, to 80 mL CH3SO3H at 70° C.-80° C. in one hour. After the addition was complete it was left at the same temperature for 15 more minutes and was then poured onto crushed ice in a beaker. Additional ice was added until the outside of the beaker felt cold to the touch. The precipitate was then collected and dissolved in 1N aqueous NaOH. Neutralization with acetic acid precipitated impurities which were removed by filtration, and acidification (HCl) of the filtrate gave isatin intermediate 4 as a solid (12.8 g, 70%). 1H NMR (400 MHz, DMSO-D6) δ ppm 2.09 (s, 3H) 2.27 (s, 3H) 6.89 (d, J=7.58 Hz, 1H) 7.25 (d, J=7.58 Hz, 1H) 11.02 (s, 1H).

Provenance & Evidence