Nickel-catalyzed conjugate addition of alkenylzirconium species to .alpha.,.beta.-unsaturated ketones

Zirconium and Hafnium: Introduction

“…a Ni(I) species from [Ni(acac)2]-DIBAH (the acetylacetonates o f Co(II) or Pd(II) are equally effective), because there is a similar selectivity as for a cuprate(I) reagent; this suggests that there may be a common intermediate, such as a ketyl, formed by a rate-determining electron transfer to the enone. 44 Similarly in the [Ni(PPh3)4] -catalyzed aryl-alkenyl cross-coupling, 40 a first-formed Ni 1 complex may be the effective initiator. In such reactions there seems to be a correlation between catalytic activity and the one-electron redox behaviour o f the catalyst as determined by cyclic voltammetry.…”

Recent Developments and Synthetic Applications of Nucleophilic Zirconocene Complexes from Schwartz's Reagent

“…After reaction optimization, the substrate scope of alkenes was evaluated, allowing the attainment of cycloketones with tertiary stereocenters (3) in low to excellent yields (between 19 and 93 %) and in good to excellent enantioselectivities (ranging from 70 to 96 % ee). The scope concerning the enones was also evaluated and the desired compounds containing 5, 6, 7 membered rings (6) were isolated in up to 75 % yield and 93 % ee. Scheme 2. Copper catalyzed ACA reaction between alkylzirconium and enones.…”

“…One of the most common uses of organozirconium derivatives is in transition metal‐catalyzed cross coupling. The usual catalyst for these reactions involves palladium and nickel . Negishi also used organozirconium chemistry in carbon–carbon bond formation through hydrozirconation reaction in the presence of alkyne to afford alkenylzirconium.…”

“…The usual catalyst for these reactions involves palladium and nickel. [6] Negishi also used organozirconium chemistry in carbon-carbon bond formation through hydrozirconation reaction in the pres-with the presence of various metals in cross-coupling reactions. Enantioselective transformations of organozirconium are described here, which have recently found wide applications in total synthesis.…”

Transmetalation Reactions Producing Organocopper Reagents

“…Transmetalation reactions of organozirconium reagents were pioneered by Schwartz [130][131][132], with improved procedures developed more recently by Lipshutz [133] and Wipf [134]. The hydrozirconation of 1-hexene with H(Cl)ZrCp 2 at 25 C under sonication conditions produces the n-hexylzirconium complex 127, which adds to cyclohexenone in the presence of CuBrÁMe 2 S (10 mol%) to afford the desired product 128 in 79% isolated yield (Scheme 2.61) [134].…”