Condensation reactions of indole with acetophenones affording mixtures of 3,3-(1-phenylethane-1,1-diyl)bis(1H-indoles) and 1,2,3,4-tetrahydro-3-(1H-indol-3-yl)-1-methyl-1,3-diphenylcyclopent[b]indoles

Condensation of indole 1a with eight acetophenones 8a-h in ethanolic HCl afforded the corresponding mixtures of condensation products: 3,3-(1-phenylethane-1,1-diyl)bis(1H-indoles) 11a-h (2:1 condensation of indole:acetophenone, -H2O) and diastereomers of substituted 1,2,3,4-tetrahydro-3-(1H-indol-3-yl)-1-methyl-1,3-diphenylcyclopent[b]indoles 12a-h and 13a-h (2:2 condensation of indole:acetophenone, -2H(2)O). Each mixture was analyzed by H-1 NMR. The use of substituted electron-withdrawing acetophenones favored formation of 2:1 condensation products, whereas the use of substituted electron-donating acetophenones favored formation of 2:2 condensation products. Increased reaction temperature gave higher 2:2 condensation yields, but temperatures above 40 degrees C were unfavorable, giving complex, tarry mixtures. [GRAPHICS] .