Piers, E. published the artcileThe decarboxylation of ring-substituted indole-2(and 3)carboxylic acids, Safety of 6-Nitro-1H-indole-3-carboxylic acid, the publication is Canadian Journal of Chemistry (1962), 559-61, database is CAplus.
A mixture of the indole-2-carboxylic acid (0.01 mole) and its Cu salt (0.0004 mole) in 10 ml. synthetic quinoline was heated until CO2 began to evolve and was kept at this temperature until gas evolution ceased (1.5-5 hrs.). The cooled solution was taken up in Et2O, washed with N HCl, H2O, Na2CO3, H2O, and dried (Na2SO4). Removal of the Et2O gave a solid, which was chromatographed on Al2O3 with CH2Cl2 as eluant. Thus, 6-Br 2-CO2H analog, decarboxylated at 210-15° in 4 hrs., yield 63%, 7-Br 2-CO2H analog, yield 74%, 4-PhCH2S 2-CO2H analog, yield 61%, 7-PhCH2S 2-CO2H analog, yield 80%, and 6-NO2 3-CO2H analog, yield 85%, were prepared The Cu salt was prepared by heating a stirred mixture of the acid (0.01 mole), Na2CO3 (0.005 mole), and H2O (100 ml.) until the acid dissolved. Upon addition of CuSO4.5H2O (0.005 mole) in 50 ml. H2O, the blue cupric salt of the indole-2-carboxylic acid precipitated The solid was washed thoroughly with H2O, air dried, then dried over CaCl2 in vacuo.
Canadian Journal of Chemistry published new progress about 10242-03-2. 10242-03-2 belongs to indole-building-block, auxiliary class Indole,Nitro Compound,Carboxylic acid,Indole, name is 6-Nitro-1H-indole-3-carboxylic acid, and the molecular formula is C9H6N2O4, Safety of 6-Nitro-1H-indole-3-carboxylic acid.
Referemce:
https://www.nature.com/articles/s41429-020-0333-2,
Preparation of Indole Containing Building Blocks for the Regiospecific Construction of Indole Appended Pyrazoles and Pyrroles