Migratory Reductive Acylation between Alkyl Halides or Alkenes and Alkyl Carboxylic Acids by Nickel Catalysis

Abstract

A mild migratory reductive acyl cross-coupling has been achieved through NiH-catalyzed chainwalking and subsequent cross-coupling from two abundant starting materials, alkyl bromides, and carboxylic acids. This strategy allows the direct acylation of the benzylic sp3 C–H bond with high yield as a single regioisomer. As an alternative, the alkyl bromide could be replaced by the proposed olefin intermediate and commercially available n-PrBr to achieve a remote hydroacylation process.

Nickel-Catalyzed Removal of Alkene Protecting Group of Phenols, Alcohols via Chain Walking Process

“…Other nickel sources such as zero valent Bis(1,5-cyclooctadiene)nickel (Ni(COD) 2 , entry 2, Table 1) or less soluble NiCl 2 (entry 3, Table 1) diminished the yield. Similar to the previous reports [31][32][33][34][35][36], more bulky ligand was critical for the reaction and probably facilitate the chain walking process (entry 4-5, Table 1). Other common phosphine ligands such as triphenylphosphine (entry 6, Table 1) and tricyclohexylphosphine (entry 7, Table 1) were all low efficient.…”

“…Other common phosphine ligands such as triphenylphosphine (entry 6, Table 1) and tricyclohexylphosphine (entry 7, Table 1) were all low efficient. Nickel(I) was proposed as the active spices in the chain walking reactions [31][32][33][34][35][36], so we tested some reductant to generate of nickel(I) spices. B 2 pin 2 in combination of base was reported as efficient reductant in nickel-catalyzed reductive reactions [47], to our pleased moderated yield was observed (entry 8, Table 1).…”

“…Meanwhile, chain walking strategy in bond construction has been emerging as a powerful tool utilizing alkene as feedstock in synthetic chemistry [22][23][24][25]. Hu [26,27], Martin [28][29][30], Zhu [31][32][33][34][35][36], and Hartwig [37] recently demonstrated that nickel was a prominent catalyst in chain walking chemistry. Streuff reported a zirconium catalyzed deallylation through chain walking mechanism [38].…”

Nickel‐Catalyzed Regioselective Hydroalkylation and Hydroarylation of Alkenyl Boronic Esters

“…Thus the Ni‐catalyzed hydrocarbonation of both terminal and internal alkenes shows linear selectivity (Scheme b). To achieve branch selectivity in NiH‐mediated alkene functionalization, an aryl directing group next to the alkenyl moiety is required (Scheme c) –. The aryl group cannot be easily removed and offers limited opportunities for further functionalization.…”

Ligand‐Enabled Nickel‐Catalyzed Redox‐Relay Migratory Hydroarylation of Alkenes with Arylborons

“…Given the abundance and easy accessibility of alkene feedstock, remote functionalization through alkene isomerization and sequential selective cross‐coupling has recently emerged as an attractive alternative in which a non‐polar C=C double bond in an arbitrary position is used as a traceless directing group and the distant C−H bond is selectively functionalized . Previously, starting from isomeric olefins and a wide variety of electrophilic coupling partners, nickel catalyzed reductive remote hydrofunctionalization has been developed via proposed nickel hydride intermediates (Figure a). Despite robust investigation, these methods are generally limited by the need of a stoichiometric amount of extra reductant.…”