Ruthenium Complexes of Phenylbenzothiazole-Quinoline based Ligands for Selective α-Olefination of Methylazaarenes

Abstract

This report describes synthesis of a new ligand (E)-N-(4-(benzo[d]thiazol-2-yl)phenyl)-1-(quinolin-2-yl)methanimine (L1) and its three ruthenium(II) arene complexes with [RuCl₂(p-cymene)]₂ (C1), [RuCl₂(benzene)]₂ (C2), and [RuCl₂(hmb)]₂ [hmb=hexamethylbenzene] (C3). The new ligand and complexes were characterized with the help of standard spectroscopic and analytical techniques like ¹H and ¹³C{¹H} Nuclear Magnetic Resonance (NMR), Fourier transform infrared (FTIR), High-resolution mass spectrometry (HRMS), UV-Visible, cyclic voltammetry, and elemental analysis. The structure of ruthenium complex (C1) and its binding mode with ligand were authenticated with the help of single crystal X-ray diffraction. The ruthenium arene complexes (C1--C3) were used as a catalyst for the α-olefination of Methylazaarenes. First, methylazaarenes were reacted with alcohols under optimized reaction conditions to produce α-olefinated products (up to 66 %) selectively. Among the three ruthenium complexes, C1 demonstrated the highest yield of olefinated products with 5 mol % catalyst loading. Finally, selected olefin derivatives were tested for their inhibitory potential towards the aggregation of amyloid-b-40 (Aβ40) peptide relevant to Alzheimer's disease. Overall, these complexes are promising catalysts for organic transformations, and the synthesized α-olefinated derivatives could have potential applications for the development of therapeutic agents for Alzheimer's disease.