REACTIONS OF ETHYL 3-ETHOXYMETHYLENE-2,4-DIOXOVALERATE AND ETHYL ETHOXYMETHYLENEOXALOACETATE WITH INDOLE ANALOGS

The reactions of ethyl 3-ethoxymethylene-2, 4-dioxovalerate (1a) and ethyl ethoxy-methyleneoxaloacetate (1b) with indole analogs (2, 14, 17-19) are described. Treatment of 1a, b with 2 in ethanol followed by refluxing in acetic anhydride afforded 3, 4, 10-trisubstituted pyrimido [1, 2-a] indoles (4a, b). Hydrogenation or nucleophilic addition of 4a, b was found to occur on the pyrimidine ring in a 1, 4-fashion. Compounds 1a, b were also reacted with 14 in ethanol under ice cooling to give the 3, 4-disubstituted 9H-pyrimido-[2, 3-b] indoles (15a, b) directly. Indole (17) or 2-methylindole (18) reacted with 1a (or 1b) to give a mixture of 3-indolylmethylene derivatives (20a, b and 21a, b) and tris-(3-indolyl)-methanes (23 and 24).