Titre: 'Unplugged' Nickel-Catalyzed C-N and C-O Cross-Couplings: DalPhos Ligand Design and Mechanistic Insights
Résumé: The relatively abundant and inexpensive nature of Ni, paired with its propensity to engage in oxidative addition, offers advantages in the quest to develop new and useful alternatives to Cu and Pd in cross-coupling catalysis. While both photochemical and electrochemical methods have been employed to promote catalytic turnover, such protocols exhibit substrate scope limitations, including poor catalytic performance with (hetero)aryl chlorides and phenol derivatives – arguably the most inexpensive and/or widely available electrophile classes. In an alternative (unplugged?) approach, my research group has explored the development of sterically demanding and modestly electron-donating bisphosphines (including the DalPhos series), which we envisioned might promote C-N/C-O reductive elimination within a putative Ni(0/II) catalytic cycle while circumventing catalyst deactivation arising from bis-chelation and/or comproportionation. Notably, the catalytic performance of Ni catalysts supported by these DalPhos ligands is often competitive with, or superior to, the best metal catalysts known (Pd, Cu, Ni, or other). The development and application of this new DalPhos ligand family, and mechanistic studies thereof, will be presented.
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