Simple and efficient Knoevenagel synthesis of (E)-2-((1H-indol-3-yl) methylene)-3-oxoindolylnitrile catalysed by PPh3

Abstract

Triphenylphosphine (TPP) is found to be an efficient catalyst for the Knoevenagel condensation of indole-3-carboxyaldehydes 1(a-e) and their N-substituted derivatives 4(a-e) with the active methylene compound, i.e., 3-cyanoacetylindole (2), affording novel substituted olefins 3(a-e) and 5(a-e) respectively. The latter products reacted with DMS in the presence of PEG-600 to afford the corresponding N, Nl dimethylated derivatives 6(a-e). © Indian Academy of Sciences.