Environmentally Benign Neat Mechanochemical Synthesis and Photophysical Studies of Indolylquinolines via Silica gel Catalyzed Metal free A3‐Coupling

An efficient neat mechanochemical method for the synthesis of fluorescent indolylquinonlines via A3‐coupling reaction of 1‐phenylsulfonylindole‐3‐carbaldehyde (1), substituted anilines 2(a–j) and substituted phenylacetylene 3(a,b) using SiO2 as an effective catalyst has been developed. The photophysical properties of newly synthesized indolylquinoline derivatives 4(a–l) were established and it depends on the nature of substituent at C6 position of quinoline moiety. A cascade method involving A3 coupling reaction catalysed by SiO2 to afford novel indolylquinolines from indole‐3‐carbaldehyde, substituted arylalkyne and substituted anilines was disclosed. Many novel indolylquinolines were synthesized under neat and mechanochemical conditions with moderate to excellent yields (69‐84%). The reaction procedure offered an environmentally amicable mild reaction conditions. The synthesized indolylquinolines were evaluated for their photophysical studies were depends upon C6 position of synthesized quinoline moiety.