Synthesis of Esters of 3-(2-Aminoethyl)-1H-indole-2-acetic Acid and 3-(2-aminoethyl)-1H-indole-2-malonic acid (= 2-[3-(2-aminoethyl)-1H-indol-2-yl]propanedioic acid) 4th communication on indoles,indolenines, and indolines

Alkyl 3-(2-aminoethyl)-1H-indole-2-acetates 6a and 6b are synthesized starting from methyl 1H-indole-2-acetate (2) via methyl 3-(2-nitroethenyl)-1H-indole-2-acetate (4) and the alkyl 3-(2-nitroethyl)-1H-indole-2-acetates 5a and (Scheme 1). Analogously, diisopropyl 3-(2-aminoethyl)-1H-indole-2-malonate 20b is obtained from diisopropyl 1H-indole-2-malonate 11c (Scheme 4). An alternative synthesis of 20a and 20b follows a route via 15–18 and the dialkyl 3-(2-azidoethyl)-1H-indole-2-malonates 19a and 19b , respectively (Scheme 3). The aminoethyl compounds 6a and 20a are easily transformed into lactams 7 and 21 , respectively. Procedures for the preparation of the indoles 2 and 11a and of the alkylating agent 14 are described. A tautomer 12 of 11a is isolated.