Ethyl 5,6-dichloro-1H-indole-2-carboxylate → 5,6-dichloro-1H-indole-2-carbaldehyde

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Reaction Conditions

Reaction Steps

Ethyl 5,6-dichloro-1H-indole-2-carboxylate (77.5 g, 301 mmol) dissolved in dry THF (70 ml) was added dropwise to an ice cold solution of LiAlH4 (19.17 g, 505 mmol) in anhydrous THF (1000 ml) under nitrogen. The mixture was stirred for 45 min at 0° C. and then quenched by the sequential addition of water (20 ml), 15% aqueous NaOH (20 ml) and water (60 ml). The mixture was filtered through-a Celite pad and then washed with THF (2×500 ml). The filtrate dried over Na2SO4 and evaporated at reduced pressure yielded an orange raw solid. This was dissolved in CH2Cl2 (1500 ml) and activated MnO2 (150 g, 1.73 mol) was added. The mixture was stirred at RT for 12 hours and then filtered through a Celite pad which was washed with warm acetone (4×750 ml), and the combined filtrates were evaporated to dryness, yielding pure title compound (42.1 g, 197 mmol, yield 65.4%), mp=207-208° C.

Provenance & Evidence