Synthesis and catalytic application of magnesium complexes bearing pendant indolyl ligands

Abstract

Three novel indole-based ligand precursors [HIndPh^R, R = methoxy, HIndPh^OMe (2a); thiomethoxy, HIndPh^SMe (2b); and N,N′-dimethylamino, HIndPh^NMe2 (2c)] have been synthesized via Sonogashira and cyclization reactions with moderate to high yield. Reactions of these ligand precursors with 0.6 equivalent of MgⁿBu₂ in THF afforded the magnesium bis-indolyl complexes 3a–3c, respectively. All the ligand precursors and related magnesium complexes have been characterized by NMR spectroscopy and elemental analyses. The molecular structures are reported for compounds 3a and 3b. Under optimized conditions, compound 3a demonstrates efficient catalytic activities towards the ring opening polymerization of L-lactide and ε-caprolactone in the presence of BnOH.