Bisphosphine‐Ligated Nickel Pre‐catalysts in C(sp²)–N Cross‐Couplings of Aryl Chlorides: A Comparison of Nickel(I) and Nickel(II)

Abstract

Thei nfluence of ancillaryl igand and nickelo xidation state in the nickel-catalyzed C(sp 2 )-Nc ross-coupling of aryl chloridesi se xamined by use of experimental andD FT methodsf or the first time, focusing on (L)NiCl and (L)Ni(o-tolyl)Clp re-catalysts (PAd-DalPhos, L1;d ppf, L2). Whereas Ni(II) pre-catalysts generally out-performed Ni(I) species in our study,t he viability and in some cases superiority of Ni(I) pre-catalysts in challenging aminations is established. Computational analyses support the viability of Ni(0)/Ni(II) cycles featuring rate-limiting C-Nr eductivee limination, as well as parallelN i(I)/ Ni(III) mechanisms involving rate-limiting C-Cl oxidative addition.

General Paradigm in Photoredox Nickel‐Catalyzed Cross‐Coupling Allows for Light‐Free Access to Reactivity

“…Our results show that Ni‐catalyzed amination, etherification, and esterification of aryl bromides can all be realized across a wide range of substrates without light under conditions that otherwise bear resemblance to the parent photochemical methodologies. To this end, one may wish to re‐evaluate the growing body of literature that invokes energy transfer as the mechanism for catalysis . As we show here, only a small amount of Ni I can initiate self‐sustained Ni I /Ni III thermal catalysis.…”

“…This supposition is supported by the observation that a sterically hindered primary amine (cyclohexylamine) could be successfully coupled ( 6 ). Given the evidence for mechanistic substrate dependence in Ni cross‐coupling reactions, the inefficiency of these recalcitrant coupling partners under our light‐free conditions may imply that the extent to which photochemical resuscitation of inactive Ni II complexes contributes to the overall observed reactivity could be similarly substrate dependent. With respect to the aryl bromide, the highest yields were obtained with those possessing electron‐deficient substituents, such as ketone ( 11 ), sulfone ( 12 ), nitrile ( 19 ), and trifluoromethyl ether ( 20 ) functionality.…”

PhPAd‐DalPhos: Ligand‐Enabled, Nickel‐Catalyzed Cross‐Coupling of (Hetero)aryl Electrophiles with Bulky Primary Alkylamines

“…In 2016 we developed the bulky and modestly electron‐donating PAd‐DalPhos bisphosphine ligand featuring a phosphaadamantane donor fragment, which we envisioned would work well in promoting rate‐limiting C−N reductive elimination within a presumptive Ni 0/II catalytic cycle . This new and modular design strategy has proven effective, with pre‐catalysts incorporating PAd‐DalPhos and related variants enabling the Ni‐catalyzed monoarylation of ammonia, unhindered primary alkylamines, as well as primary amides and lactams, with a diversity of (hetero)aryl (pseudo)halides.…”

Preise des Chemical Institute of Canada und der Canadian Society for Chemistry

“…Johnson untersucht elektronische Strukturen mithilfe von Dichtefunktionaltheorie; unter ihren Studienobjekten sind London‐Dispersionswechselwirkungen, Molekülkristalle, Schichtmaterialien, Elektride und metallorganische Komplexe. Ein Beitrag von ihr in Advanced Synthesis & Catalysis behandelt Nickel‐Präkatalysatoren für Kreuzkupplungen . Johnson wurde außerdem 2018 mit der Dirac‐Medaille der World Association of Theoretical and Computational Chemists (WATOC) ausgezeichnet.…”