Environmentally friendly synthesis and computational studies of novel class of acridinedione integrated spirothiopyrrolizidines/indolizidines

An efficient and environmentally benign synthesis of a new class of acridinedione embedded spirooxindolo/acenaphthenothiopyrrolizidines and spirooxindolo/acenathenoindolizidines has been synthesized in good to excellent yields employing ionic liquid accelerated one-pot [3 + 2]-cycloaddition strategy. The pre-requisite starting substrates, O-acryloyl acridinediones were prepared from dimedone in three good yielding steps, while the 1,3-dipole was derived in situ from isatin/acenaphthenequinone and thiazolidine-4-carboxylc acid/l-pipecolinic acid via decarboxylative condensation. The cycloadduct possesses three stereogenic carbons, one of which is a spiro carbon through the formation of two C–C and one C–N bonds in one-pot synthetic transformation. Geometrical parameters of the synthesized compounds were calculated using the B3LYP/6-311g(d,p) level of theory. The activity of these molecules was evaluated against main protease of COVID-19 to screen them for their inhibitor efficiency. In order to get a broad understanding of the interactions of these synthesized ligands, a detailed molecular docking analysis was performed. Molecular docking analysis shows that compound 8b has the highest binding affinity toward the protein. The compound can be a potential candidate for the treatment of COVID-19.