A revisit to the multi-component reaction of indole, aldehyde, and N -substituted aniline catalyzed by PMA–SiO 2

PMA–SiO2-catalyzed multi-component reaction of indole, aromatic aldehyde, and N-substituted aniline at room temperature under solvent-free condition is reported here. The reaction was previously reported, where a C–C and C–N bond were formed. However, we established a different structure for the product with the help of NMR as well as single-crystal X-ray studies, where the C-4 atom of N-substituted aniline is linked to the aldehydic carbon, and consequently, two new C–C bonds are formed. The mechanism of the reaction is established through trapping of the intermediate which is also different from the previous report. To the best of our knowledge, only one report is available in the literature for the synthesis of this class of important compounds.