Synthesis of 2-(2,2-dimethyl-1-oxopropyl)-indole-3-carboxylic acid by the indoledione-indole rearrangement method in NaOH/AQ. DMSO

l-(2-Oxoalkyl)indole-2,3-diones (la-f) undergo the indoledione-indole rearrangement in 0.4-1% aq. NaOH to give the sodium salt of the corresponding 2-(l-oxoalkyl)indole-3-carboxylic (Ila-f) [1-4]. Under the same conditions, only opening of the heterocycle occurs in the case of l-(3,3-dimethyl-3-oxobutyl)indole-2,3-dione (Ig) to give the Na salt of 2-(3,3-dimethyl-2-oxobutyl)phenyloxoacetic acid (III). !