The formylation of 3-alkylindole-2-acetic esters

Methyl 22-(3- methyl)indolyl]acetate (1a), on treatment with sodium hydride and methyl formate, gives methyl (Z) - 22 - (3 - methyl)indolyl] - 3 - hydroxyacrylate (2a), which is in tautomeric solvent-dependent equilibrium with methyl 22 - (3 - methyl)indolinylidene] - 3 - oxopropanoate (6). On reaction with phosphoryl chloride in dimethyl formamide, (1a) yields methyl (Z) - 22 - (3 - methyl)indolyl] - 3 - N,N - dimethylaminoacrylate (9) as expected, together with a more complex product derived from (9).