New Strategy for Indole Synthesis from Ethyl Pyrrole-2-carboxylate (Synthetic Studies on Indoles and Related Compounds. XXXIX)

As a synthetic application of the previously reported C4-acylation of ethyl pyrrole-2-carboxylate (1), a new strategy for indole synthesis was developed. Ethyl pyrrole-2-carboxylate (1) was allowed to react with succinic anhydride or 3-methoxycarbonylpropionyl chloride to give, in good yield, a C4-succinyl derivative of 1, which was converted into ethyl 7-oxo-4, 5, 6, 7-tetrahydroindole-2-carboxylate (6) as a key intermediate for indole synthesis. Starting from 6, several indoles functionalized on the benzene moiety were synthesized.