Ammonia → 4-bromo-2-methyl-2,3-dihydro-1H-indole

Participants

Reaction Conditions

Reaction Steps

7.99 g of sodium cyanoborohydride are gradually added to a solution of 8.90 g of 4-bromo-2-methylindole (which can be prepared according to patent US2010/160647 A1, 2010) in 310 ml of acetic acid under argon cooled to a temperature of about 14° C. The reaction mixture is stirred at a temperature of about 14° C. for 15 minutes, and it is then allowed to warm up to ambient temperature. After 2 hours, the reaction mixture is poured into an Erlenmeyer flask containing ice-cold water (200 ml) and then the pH is brought to 9 with an aqueous ammonia solution. The reaction medium is extracted with dichloromethane (2×200 ml) and then the organic phases are combined, washed with water, dried over magnesium sulfate, filtered, and then concentrated to dryness under reduced pressure. After purification of the residue by silica column chromatography, elution being carried out with a mixture of heptane and ethyl acetate (90/10), 5.92 g of 4-bromo-2-methylindoline are obtained, the characteristics of which are the following:

Provenance & Evidence