Dimethyl Carbonate → 1-ethyl-5-(2-methyl-[1,3]dioxolan-2-yl)-2-oxo-2,3-dihydro-1H-indole-3-carboxylic acid methyl ester

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Reaction Steps

Sodium (2.68 g, 112 mmol) was added to methanol (110 mL) in a 3-neck flask fitted with a reflux condenser, while controlling the temperature with an ice-bath. After dissolution dimethyl carbonate (9.4 mL, 112 mmol) was added followed by 1-ethyl-5-(2-methyl-[1,3]dioxolan-2-yl)-1,3-dihydro-indol-2-one (U.S. Pat. No. 4,686,224, 9.2 g, 37 mmol). The mixture was heated to reflux for 70 hours, then cooled, concentrated to about 25 mL, diluted with water, acidified to pH 7 with acetic acid and extracted twice with ethyl acetate. The combined extracts were washed with brine, dried over magnesium sulfate and concentrated in vacuo to an oily solid which was triturated in isopropyl ether, collected and dried (7.9 g, 70%).

Provenance & Evidence