Ni(COD)(DQ): An Air‐Stable 18‐Electron Nickel(0)–Olefin Precatalyst

Abstract

We report that Ni(COD)(DQ) (COD = 1,5-cyclooctadiene, DQ = duroquinone), an air-stable 18-electron complex originally described by Schrauzer in 1962, is a competent precatalyst for a variety of nickel-catalyzed synthetic methods from the literature. Due to its apparent stability, use of Ni(COD)(DQ) as a precatalyst allows reactions to be conveniently performed without use of an inert-atmosphere glovebox, as demonstrated across several case studies. Scheme 1. Overview of the growing nickel precatalyst toolkit.

Stereospecific, Ligand-Free Synthesis of All-Carbon Quaternary Stereocenters from Tertiary Benzylic Carboxylates

“…Ester Scope In terms of mechanism, we hypothesize that this reaction proceeds via a Ni 0/II catalytic cycle, starting with oxidation addition via an SN2'-like attack of a Ni 0 species on the benzylic carboxylate. 14,17 The overall reaction proceeds with stereoretention, 22 consistent with oxidative addition through a closed transition state with the carboxylate directing Ni 0 to the ortho position of the aryl ring. Subsequent transmetallation and reductive elimination delivers product and completes the catalytic cycle.…”

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

“…When Ni(cod) 2 was replaced with airstable Ni(cod)(DQ) and the reaction was set up outside of the glovebox, 76 %y ield (2aa)a nd 16 %y ield (3aa)w ere obtained using L19 and no ligand, respectively (see SI for details). [15] After identifying conditions for both Markovnikov and anti-Markovnikov selectivity,w en ext examined the scope and limitations of both protocols.W ef irst explored the anti-Markovnikov-selective protocol with ligand L19 ( Table 2). In terms of arylboronic acids,the presence of electron-donating and -withdrawing groups at the para and meta position did not affect the yield and selectivity (2aa-2ae, 2aj-2ao).…”

“…However, introduction of an electron‐withdrawing substituent completely shut down the reaction. When Ni(cod) 2 was replaced with air‐stable Ni(cod)(DQ) and the reaction was set up outside of the glovebox, 76 % yield ( 2 aa ) and 16 % yield ( 3 aa ) were obtained using L19 and no ligand, respectively (see SI for details) [15] …”

Stereospecific, Ligand-Free Synthesis of All-Carbon Quaternary Stereocenters from Tertiary Benzylic Carboxylates

“…Using pivalates and increasing the reaction temperature to 80 °C enabled efficient cross-couplings of simple phenyl-substituted esters (19−21). Additionally, more sterically hindered quaternary centers (22,23) were also accessible. The ability to incorporate heteroaryls and non-naphthyl substituents dramatically expands the utility of this method.…”