One-Pot, Step-Wise, Alternative Syntheses of Quinoline-Substituted Bis(Indolyl)Methanes Using a Green Approach

A green and highly efficient protocol for one-pot, step-wise, alternative syntheses of quinoline-substituted bi(indolyl)methanes has been described by the condensation of N-methyl or N-ethyl quinolone-4-one-3-carbaldehydes 1a and b with indole 2a–f in water containing a catalytic amount of l-proline to afford the title compounds 5a–l in high yields and in shorter reaction times. This reaction involves easy workup without using column chromatography.