Distinguishing Competing Mechanistic Manifolds for C(acyl)-N Functionalization by a Ni/ N -Heterocyclic Carbene Catalyst System.

Autor:	Malyk KR; University of Rochester, Department of Chemistry, Rochester, New York 14627, United States., Pillai VG; University of Rochester, Department of Chemistry, Rochester, New York 14627, United States., Brennessel WW; University of Rochester, Department of Chemistry, Rochester, New York 14627, United States., Leon Baxin R; University of Rochester, Department of Chemistry, Rochester, New York 14627, United States., Silk ES; University of Rochester, Department of Chemistry, Rochester, New York 14627, United States., Nakamura DT; University of Rochester, Department of Chemistry, Rochester, New York 14627, United States., Kennedy CR; University of Rochester, Department of Chemistry, Rochester, New York 14627, United States.
Jazyk:	angličtina
Zdroj:	JACS Au [JACS Au] 2023 Aug 21; Vol. 3 (9), pp. 2451-2457. Date of Electronic Publication: 2023 Aug 21 (Print Publication: 2023).
DOI:	10.1021/jacsau.3c00283
Abstrakt:	Carboxylic acid derivatives are appealing alternatives to organohalides as cross-coupling electrophiles for fine chemical synthesis due to their prevalence in biomass and bioactive small molecules as well as their ease of preparation and handling. Within this family, carboxamides comprise a versatile electrophile class for nickel-catalyzed coupling with carbon and heteroatom nucleophiles. However, even state-of-the-art C(acyl)-N functionalization and cross-coupling reactions typically require high catalyst loadings and specific substitution patterns. These challenges have proven difficult to overcome, in large part due to limited experimental mechanistic insight. In this work, we describe a detailed mechanistic case study of acylative coupling reactions catalyzed by the commonly employed Ni/SIPr catalyst system (SIPr = 1,3-bis(2,6-di-isopropylphenyl)-4,5-dihydroimidazol-2-ylidine). Stoichiometric organometallic studies, in situ spectroscopic measurements, and crossover experiments demonstrate the accessibility of Ni(0), Ni(I), and Ni(II) resting states. Although in situ precatalyst activation limits reaction efficiency, the low concentrations of active, SIPr-supported Ni(0) select for electrophile-first (closed-shell) over competing nucleophile-first (open-shell) mechanistic manifolds. We anticipate that the experimental insights into the nature and controlling features of these distinct pathways will accelerate rational improvements to cross-coupling methodologies involving pervasive carboxamide substrate motifs. Competing Interests: The authors declare no competing financial interest. (© 2023 The Authors. Published by American Chemical Society.)
Databáze:	MEDLINE
Externí odkaz:	Zobrazit plný text záznamu