Catalyst‐Free and Metal‐Free Approach towards Synthesis of Amide‐ and Thioamide‐Linked β‐Carboline‐Pyridine Conjugates and Estimation of Their Photophysical Properties

Abstract

AbstractA series of novel β‐carboline‐pyridine conjugates linked though amide and thioamide tethers were synthesized under catalyst‐free and metal‐free conditions using β‐carboline alkaloid; Kumujian C as a template. The tert‐butyl hydroperoxide (TBHP)‐mediated reaction with 2‐aminopyridines provided the amide linked β‐carboline‐pyridine conjugates whereas the Willgerodt‐Kindler reaction in presence of elemental sulfur furnished thioamide tethered analogues. The alkyl, aryl, as well as heteroarylamines underwent Willgerodt‐Kindler reaction with Kumujian C to afford diverse β‐carboline linked thioamides. Both the protocols avoided the use of toxic metal catalysts and expensive additives to provide the products in moderate to excellent yields in a short duration. Interestingly, the amide linked β‐carboline‐pyridine conjugates displayed excellent photophysical properties with fluorescence quantum yields (ΦF) up to 38% rendering them as promising candidates for applications in biology and optoelectronic materials.