Redox‐Neutral Nickel(II) Catalysis: Hydroarylation of Unactivated Alkenes with Arylboronic Acids

Abstract

Reported here is the discovery of a redox-neutral Ni II /Ni II catalytic cycle which is capable of the linear-selective hydroarylation of unactivated alkenes with arylboronic acids for the first time. This novel catalytic cycle, enabled by the use of an electron-rich diimine ligand, features broad substrate scope, and excellent functional-group and heterocycle compatibility under mild reaction conditions in the absence of additional oxidants and reductants. Mechanistic investigations using kinetic analysis and deuterium-labelling experiments revealed the protonation to be the rate-determining step in this redox-neutral catalysis, and the reversible chain-walking nature of the newly developed diimine-Ni catalyst.

Ligand‐Controlled Regiodivergence in Nickel‐Catalyzed Hydroarylation and Hydroalkenylation of Alkenyl Carboxylic Acids**

“…Recently,n ickel catalysis has emerged as ap owerful means of effecting alkene hydroarylation. [4,5,7] In particular, redox-neutral coupling of arylboronic acids and alkenes (Scheme 1B) [9][10][11] is attractive in that it combines programmed reactivity at the ArÀBb ond with operationally simple reaction conditions and does not require stochiometric silane reductants (as in R À X/R 3 Si À Hs ystems). [5, 6e-g, 7] Originally pioneered by Zhou and co-workers,s uch reaction systems have been largely limited to conjugated alkenes,s uch as styrenes and 1,3-dienes,w here regioselectivity is dictated by the stability of the corresponding p-benzyl/allyl intermediate.…”

Ni-catalyzed hydroalkylation of olefins with N-sulfonyl amines

“…In this respect, advances in nickel-complex-catalyzed hydrocarbonation of olefins have expanded the chemical space of accessible structures and enabled new synthetic disconnections [17][18][19][20][21] . Compared with hydroarylation [22][23][24][25][26][27][28][29][30][31][32][33][34] and hydroalkenylation 26,32,35 , hydroalkylation produces molecules that are richer in sp 3 -hybridized carbon centers and contain more stereogeometric information [36][37][38][39][40][41][42] , a feature that may improve biological activity 43,44 . In the 1990s, Mori disclosed intramolecular C(sp 3 )-C(sp 3 ) bond formation reactions between conjugated dienes and carbonyl groups with catalysis by a nickel hydride complex generated by treatment of Ni(cod) 2 with Et 3 SiH 45 .…”

Ligand-Enabled Ni-Catalyzed Hydroarylation and Hydroalkenylation of Internal Alkenes with Organoborons

“…In the context of our recent efforts on Ni-catalyzed hydroarylation of unactivated alkenes, we found the redox-neutral Ni (II)-catalysis is capable of the hydroarylation of cyclohexene and 1,1-disubsituted alkenes, albeit with lower efficiency. 60 Hence, we envisioned that the more challenging hydroarylation of 1,2disubsituted internal alkenes could be realized via a ligand acceleration approach using nickel as the catalyst under redox-neutral conditions. Unfortunately, the hydroarylation for the 1,2-disubstituted alkene didn't proceed in the presence of Ni(acac)2 and electron-rich diamine ligand L1, which is superior in the redoxneutral Ni(II)-catalyzed hydroarylation of unactivated alkene.…”

“…Moreover, the Ni(COD)2 is also an effective catalyst for this hydroarylation reaction, unlike our previous Ar-Ni(II) initiated reaction where the Ni(COD)2 is inactive. 60 The kinetic studies are next conducted by the reaction progress kinetic analysis, revealing that this reaction is zero order to alkene and arylboronic acid and first order with regard to Ni(2-NH2-5-MeC6H3SO3)2/L14 catalyst (Fig. 6c and Fig.…”