Abstract:A mild cobalt-catalyzed Negishi-type cross-coupling of various functionalized dialkylzinc reagents with primary and secondary alkyl iodides in acetonitrile is reported using a combination of 20% CoCl 2 and chelating nitrogen ligands. The method allows the construction of molecules with alkyl chains bearing sensitive functional groups at room temperature.
“…Although in comparatively lower yields than those shown in Fig. 2 , these results should be benchmarked against the challenge of catalytic C( sp 3 ) - C( sp 3 ) cross-coupling by offering a complementary technique to existing approaches 65 – 67 . Fig.…”
C–C bond forming cross-couplings are convenient technologies for the construction of functional molecules. Consequently, there is continual interest in approaches that can render traditionally inert functionality as cross-coupling partners, included in this are ketones which are widely-available commodity chemicals and easy to install synthetic handles. Herein, we describe a dual catalytic strategy that utilizes dihydroquinazolinones derived from ketone congeners as adaptative one-electron handles for forging C(sp3) architectures via α C–C cleavage with aryl and alkyl bromides. Our approach is achieved by combining the flexibility and modularity of nickel catalysis with the propensity of photoredox events for generating open-shell reaction intermediates. This method is distinguished by its wide scope and broad application profile––including chemical diversification of advanced intermediates––, providing a catalytic technique complementary to existing C(sp3) cross-coupling reactions that operates within the C–C bond-functionalization arena.
“…Although in comparatively lower yields than those shown in Fig. 2 , these results should be benchmarked against the challenge of catalytic C( sp 3 ) - C( sp 3 ) cross-coupling by offering a complementary technique to existing approaches 65 – 67 . Fig.…”
C–C bond forming cross-couplings are convenient technologies for the construction of functional molecules. Consequently, there is continual interest in approaches that can render traditionally inert functionality as cross-coupling partners, included in this are ketones which are widely-available commodity chemicals and easy to install synthetic handles. Herein, we describe a dual catalytic strategy that utilizes dihydroquinazolinones derived from ketone congeners as adaptative one-electron handles for forging C(sp3) architectures via α C–C cleavage with aryl and alkyl bromides. Our approach is achieved by combining the flexibility and modularity of nickel catalysis with the propensity of photoredox events for generating open-shell reaction intermediates. This method is distinguished by its wide scope and broad application profile––including chemical diversification of advanced intermediates––, providing a catalytic technique complementary to existing C(sp3) cross-coupling reactions that operates within the C–C bond-functionalization arena.
“…Furthermore, ring closures and openings indicated the occurance of radical intermediates in the course of such cross-couplings (see Scheme 10 ). 32 …”
Section: Reactions Of Polyfunctional Organozinc Reagentsmentioning
Polyfunctional organometallics of magnesium and zinc are readily prepared from organic halides via a direct metal insertion in the presence of LiCl or a Br/Mg-exchange using iPrMgCl·LiCl (turbo-Grignard) or related...
“…Knochel and co-workers reported the coupling of primary and secondary alkyl iodides with primary dialkylzinc reagents in the presence of CoCl 2 (20 mol %), either neocuproine or trans - N , N , N ′, N ′-tetramethylcyclohexane-1,2-diamine (20 mol %) as the ligand, and tetrabutylammonium iodide as an additive in MeCN at room temperature (Scheme ). The reported method is mild and compatible with a wide variety of functionalized alkylzinc reagents (acetates, carbamates, esters, nitrile, etc.). The products were isolated in synthetically useful yields, and this method complements the known Pd- and Ni-catalyzed C(sp 3 )–C(sp 3 ) cross-coupling methods well. − …”
Section: Recent Reports On Co-catalyzed Reactionsmentioning
This
highlight is the second installment of a series of highlights on nonprecious-metal-catalyzed
reactions of interest to the pharmaceutical industry. Selected transformations
from March to June 2020 are summarized. Our goal is to facilitate
advancements in the areas of safer and greener chemical manufacturing
using earth-abundant metals.
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