Abstract
A strategy is put forward to generate meta-terphenyl ligands that can be recycled and reused, demonstrated through ligand synthesis, halogenation, metalation and recovery of one example.
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5-pyrrolidino-m-terphenyl (1) is synthesized via a Buchwald-Hartwig cross-coupling reaction. This terphenyl is readily halogenated under ambient conditions with tetrabutylammonium tribromide to generate 4-pyrrolidino-2,6-diphenylbromobenzene (2). The reaction of (2) with magnesium results in the conversion to its corresponding Grignard reagent (3). Quenching of (3) with water results in the recovery of (1), demonstrating the ability to recycle this m-terphenyl ligand through a halogenation-metalation-hydrolysis cycle. The structure of all three compounds were confirmed by 1H and 13C NMR and by single-crystal X-ray diffraction.