Yang J, Neary MC, Diao T. ProPhos: A Ligand for Promoting Nickel-Catalyzed Suzuki-Miyaura Coupling Inspired by Mechanistic Insights into Transmetalation.
J Am Chem Soc 2024;
146:6360-6368. [PMID:
38391156 PMCID:
PMC10921396 DOI:
10.1021/jacs.4c00370]
[Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2024] [Revised: 02/05/2024] [Accepted: 02/07/2024] [Indexed: 02/24/2024]
Abstract
Nickel-catalyzed Suzuki-Miyaura coupling (Ni-SMC) offers the potential to reduce the cost of pharmaceutical process synthesis. However, its application has been restricted by challenges such as slow reaction rates, high catalyst loading, and a limited scope of heterocycles. Despite recent investigations, the mechanism of transmetalation in Ni-SMC, often viewed as the turnover-limiting step, remains insufficiently understood. We elucidate the "Ni-oxo" transmetalation pathway, applying PPh2Me as the ligand, and identify the formation of a nickel-oxo intermediate as the turnover-limiting step. Building on this insight, we develop a scaffolding ligand, ProPhos, featuring a pendant hydroxyl group connected to the phosphine via a linker. The design preorganizes both the nucleophile and the nickel catalyst, thereby facilitating transmetalation. This catalyst exhibits fast kinetics and robust activity across a wide range of heteroarenes, with a catalyst loading of 0.5-3 mol %. For arene substrates, the catalyst loading can be further reduced to 0.1 mol %.
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