Ishii, Hisashi published the artcileAbnormal Fischer indolization and its related compounds. XII. Synthesis of 3,6′-biindole, Application In Synthesis of 20538-12-9, the publication is Chemical & Pharmaceutical Bulletin (1979), 27(2), 346-50, database is CAplus.
Fisher indole reaction of Et indole-2-carboxylate with (E)-2-MeOC6H4NHN:CMeCO2Et (I) in refluxing C6H6 containing MeC6H4SO3H gave 12.2% Et 7-methoxyindole-2-carboxylate and 28.4% biindole II (R = CO2Et). Saponification of II (R = CO2Et) gave II (R = CO2H) which was decarboxylated by heating in quinoline containing Cu-chromite to give 3,6′-diindole (II; R = H). Treatment of indole with I in refluxing C6H6 containing MeC6H4SO3H gave 11.3% Z–I, 25.6% diindolylpropionate III, and 17.3% indole trimer IV.
Chemical & Pharmaceutical Bulletin published new progress about 20538-12-9. 20538-12-9 belongs to indole-building-block, auxiliary class Indole,Ester,Ether, name is Ethyl 7-methoxy-1H-indole-2-carboxylate, and the molecular formula is C12H13NO3, Application In Synthesis of 20538-12-9.
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