Hβ zeolite-mediated sustainable solvent free synthesis of indole-2-carboxylic esters

This study presents a novel, sustainable approach for the synthesis of indole-2-carboxylic esters using H-beta zeolite as a heterogeneous catalyst under solvent-free conditions. The method employs readily available 2-vinyl anilines and dialkyl acetylenedicarboxylates as starting materials, addressing the limitations of traditional synthetic routes. H-beta zeolite demonstrated superior catalytic activity compared to other zeolites, attributed to its unique pore structure and acidic properties. The solvent-free conditions and heterogeneous nature of the catalyst align with green chemistry principles, offering advantages such as reduced waste generation, simplified product isolation, and catalyst recyclability. Optimization of reaction parameters, including catalyst loading and temperature, yielded the desired indole-2-carboxylic esters in good to excellent yields. The catalyst showed excellent recyclability, maintaining its activity over multiple cycles.