Self-Assembled Lanthanide Supramolecular Helicates: Efficient Catalysts for Synthesis of Heterocyclic Scaffolds

Abstract

Geometrically unsaturated binuclear double-stranded metallohelicates constructed with pyridyl hydrazine ligands and lanthanide metal ions via metal-templated self-assembly. The single-crystal X-ray analysis suggests the formation of helical assembly through its coordination with pyridyl, azomethine nitrogen’s and ketonic oxygen with metal ions. Lanthanide ions are known to possess multiple coordination sites, other labile sites are occupied with solvents and anions. The lanthanide helicates are exhaustively characterized and adopted as a catalyst to synthesize benzothiazole scaffolds starting from 2-fluoroaniline and phenyl isothiocyanate substrates via tandem thiourea intermediate/cyclization pathway. The mechanistic investigation suggests the reaction proceeds via the nucleophilic aromatic substitution pathway. The protocols are extended for the synthesis of drug molecules such as Riluzole and Dimazole.