Indole-2-carboxaldehyde → 5-tert-butoxycarbonylamino-3-(1H-indol-2-ylmethylene)-1,3-dihydro-indol-2-one

Participants

Reaction Conditions

Reaction Steps

A mixture of 5-tert-butoxycarbonylamino-2-oxindole (124 mg), indole-2-carbaldehyde (87 mg) (prepared according to Synthetic Communications, 1993, 23, 3109) and piperidine (4 mg) in ethanol (2 mL was heated in a sealed tube at 90° C. for 3 hours. The mixture was cooled to room temperature. The solid was collected by vacuum filtration, washed with cold ethanol and dried in oven for overnight to give 196 mg of 5-tert-butoxycarbonylamino-3-(1H-indol-2-ylmethylene)-1,3-dihydro-indol-2-one as a bright orange solid. It was then dissolved in trifluoroacetic acid/dichloromethane mixture (2 mL each) and stirred at room temperature for 1 hour. The reaction mixture was concentrated. The residue was dissolved in water and basified with saturated sodium bicarbonate solution. The solid was collected by vacuum filtration, washed with water and dried in vacuum oven for overnight to give 129 mg of 5-amino-3-(1H-indol-2-ylmethylene)-1,3-dihydro-indol-2-one as a brown solid.

Provenance & Evidence