Precatalyst Effects on Pd-Catalyzed Cross-Coupling Difluoromethylation of Aryl Boronic Acids
The Pd-catalyzed difluoromethylation of aryl boronic acids with difluoroiodomethane is shown to provide the difluoromethyl compounds in high to moderate yields by Pd(PPh3)2/DPEphos catalyst in H2O/toluene. Mechanistic studies show that the oxidative addition by Pd(PPh3)4 rather than Pd2(dba)3 prec...
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Veröffentlicht in: | ACS catalysis 2019-01, Vol.9 (1), p.417-421 |
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Hauptverfasser: | , , , |
Format: | Artikel |
Sprache: | eng |
Online-Zugang: | Volltext |
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Zusammenfassung: | The Pd-catalyzed difluoromethylation of aryl boronic acids with difluoroiodomethane is shown to provide the difluoromethyl compounds in high to moderate yields by Pd(PPh3)2/DPEphos catalyst in H2O/toluene. Mechanistic studies show that the oxidative addition by Pd(PPh3)4 rather than Pd2(dba)3 precatalyst to difluoroiodomethane provides a square-planar trans-(PPh3)2Pd(II)(CF2H)I complex defined by X-ray crystallographic analysis. The trans-(PPh3)2Pd(CF2H)I complex is transformed to cis-(PPh3)2Pd(CF2H)Ph detected by low temperature NMR analysis, via transmetalation with phenylboronic acids. The reductive elimination occurs via ligand exchange to DPEphosPd(CF2H)Ph to give Ph–CF2H (t 1/2 = 144.7 min at 20 °C) with formation of the Pd(0)(PPh3)2/DPEphos catalyst. |
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ISSN: | 2155-5435 2155-5435 |
DOI: | 10.1021/acscatal.8b03892 |