Ferric chloride mediated synthesis, photophysical and in vitro anti-Alzheimer's properties of 1H-pyrrolo[2,3-b]pyridin-3-ylmethylphenyl-2-(9H-fluoren-9-ylidene)-1-phenylethan-1-imines

Abstract

Among several Lewis acids tested, ferric chloride has emerged as an efficient Lewis acid catalyst for the reaction of 9-fluorene propargylic alcohols with 2-(7-azaindole-3-methelene) aniline as the nucleophile, affording various substituted 7-azaindole-appended 2-(9H-fluoren-9-ylidene)-1-phenylethan-1-imine derivatives in good yields. The scope, limitations of the reaction, characterization of the products including single crystal XRD, and a plausible mechanism for the formation of the products are provided. Photophysical properties and a detailed in vitro bioactivity were evaluated for selected derivatives. All the selected compounds exhibited two emissions in the blue region, and a few of the synthesized compounds showed enhanced antioxidant activity (IC₅₀: 25–35 µg mL⁻¹) and inhibited acetylcholinesterase (AChE) (∼30 µg mL⁻¹) in Neuro-2a cells. They also exhibited cytotoxicity (IC₅₀: 28–67 µg mL⁻¹) and effectively reduced intracellular reactive oxygen species (ROS) levels. These results highlight the potential of this novel scaffold as a multifunctional neuroprotective and anti-Alzheimer's agent.