Benzyl 4-[di(ethoxycarbonyl)methoxy]indole-1-carboxylate → Diethyl 2-(indol-4-yloxy)malonate

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Reaction Steps

A solution of 12 (8.51 g, 20 mmol) in ethanol (250 mL) was mixed with 10% palladium on carbon (1.5 g) and hydrogenated at atmospheric pressure for 1 h until hydrogen uptake ceased. The catalyst was filtered off through a Celite bed and washed with ethanol, and the filtrate was evaporated to give a brown oil. Filtration through flash silica with ethyl acetate-hexanes (3:2) as eluent, followed by trituration with diethyl ether-hexanes at −20° C. gave 8 as white crystals (4.78 g, 82%), mp 52-53° C. (from diethyl ether-hexanes), identical to the material described above.

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