Di-tert-butyl dicarbonate → 1-t-Butoxycarbonyl-2,3-dihydro-7-methyl-6-nitroindole

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Reaction Steps

The isomeric mixture of 2,3-dihydro-7-methyl-6-nitroindole and 2,3-dihydro-7-methyl-4-nitroindole (6.10 g; 0.0337 mol) is dissolved in methylene chloride (50 mL). To this solution is added N,N-dimethylaminopyridine (4.30 g; 0.0337 mol) and di-t-butyidicarbonate (22.5 g; 0.101 mol). Additional methylene chloride (50 mL) is added and the flask is equipped with a reflux condenser. The solution is allowed to stir overnight under an atmosphere of argon. The methylene chloride solution is extracted with four 100-mL portions of aqueous citric acid and is dried over anhydrous potassium carbonate. The solution is filtered, concentrated by rotary evaporation and dried under vacuum to give an oily, brown solid. The crude mixture is purified by silica gel flash column chromatography using 5% ethyl acetate/hexanes as eluent to give 2.44 g of 1-t-butoxycarbonyl-2,3-dihydro-7-methyl-4-nitroindole as a yellow solid and 2.6 g of 1-t-butoxycarbonyl-2,3-dihydro-7-methyl-6-nitroindole as well as some unseparated material.

Provenance & Evidence