On Ni Catalysts for Catalytic, Asymmetric Ni/Cr-Mediated Coupling Reactions

Abstract

The importance of the Ni catalyst in achieving catalytic asymmetric Ni/Cr-mediated coupling reactions effectively is demonstrated. Six phenanthroline-NiCl(2) complexes 1a-c and 2a-c and five types of alkenyl iodides A-E were chosen for the study, thereby demonstrating that these Ni catalysts display a wide range of overall reactivity profiles in terms of the degree of asymmetric induction, geometrical isomerization, and coupling rate. For three types of alkenyl iodides A-C, a satisfactory Ni catalyst(s) was found within 1a-c and 2a-c. For disubstituted (Z)-alkenyl iodide D, 2c was identified as an acceptable Ni catalyst in terms of the absence of Z → E isomerization and the degree of asymmetric induction but not in terms of the coupling rate. Two phosphine-based Ni catalysts, [(Me)(3)P](2)·NiCl(2) and [(cy)(3)P](2)·NiCl(2), were found to meet all three criteria for D. The bond-forming reaction at the C16-C17 position of palytoxin was used to demonstrate the usefulness of the Ni catalysts thus identified.

Nickel-Catalyzed Reductive Couplings

“…A stoichiometric reaction of allyl carbonate, benzaldehyde and Ni 0 -L n in the absence of Zn was able to produce the product in a similar yield and ee to the catalytic conditions, suggesting allyl-Ni may be the key intermediate for the allylation event. This is distinctive from the Nozaki-Hiyama-Kishi reactions [84]. In addition, the 1-or 3-phenyl-substituted allyl carbonate gave the product in moderate yield and ee at -25°C but with high anti/syn selectivities.…”

Catalytic Asymmetric Synthesis of Allylic Alcohols and Derivatives and their Applications in Organic Synthesis

“…Recently, Kishi and co-workers studied the influence of the Ni II source on the addition of (Z)-disubstituted alkenyl iodide 176 to 171 (Scheme 77). [176] They found that the coupling required less than two hours when [{(Me) 3…”

“…The use of ligand 138, which contains binding sites for both metals and thus places them in proximity, allowed significant reductions in both the amount of chromium used (1-2 mol %) and the molar ratio of the coupling partners (171/ 172 1:1 to 1:1.1). [176] They found that the coupling required less than two hours when [{(Me) 3 [172] The great efficiency of these new ligands has been demonstrated in the total synthesis of various challenging natural products and intermediates, [173] including building blocks of E7389 and halichondrin B/C [174] (Figure 6 and Schemes 74 and 75) as well as aplyrorine A-mycalolide B hybrid compound [175] (Figure 6, Recently, Kishi and co-workers studied the influence of the Ni II source on the addition of (Z)-disubstituted alkenyl iodide 176 to 171 (Scheme 77).…”

A CuI‐Based Metallo‐Supramolecular Gel‐Like Material Built from a Library of ­Oligomeric Ligands Featuring Exotopic 1,10‐Phenanthroline Units

“…2,9-Dimethyl-4,7-bis(oct-7-enyloxy)-1,10-phenanthroline (3) was synthesized as shown below, adapting a literature procedure. [31] The NaH dispersion in mineral oil was washed with hexane immediately prior to use. THF was distilled from sodium and benzophenone.…”