Synthesis
Tert-butyl 6-(hydroxymethyl)indoline-1-carboxylate (163 mg, 0.654 mmol) was used as a raw material and dissolved in 3.2 mL of anhydrous dichloromethane. To this solution was added Dess-Martin periodinane (290 mg, 0.68 mmol) at room temperature. The reaction mixture was stirred at the same temperature for 30 min before the reaction was terminated by adding saturated aqueous NaHCO3 solution. Subsequently, the reaction mixture was extracted with ethyl acetate and the organic phase was washed with brine and dried with anhydrous MgSO4. After filtration to remove the desiccant, the filtrate was concentrated under reduced pressure. The residue was purified by silica gel column chromatography with an eluent ratio of hexane/ethyl acetate (95/5 to 75/25) to afford tert-butyl 6-formylindoline-1-carboxylate as a white powder (140 mg, 86% yield).
References
[1] Patent: EP2123637, 2009, A1. Location in patent: Page/Page column 80
[2] Patent: US2003/232860, 2003, A1. Location in patent: Page 20
