Hydroarylations by cobalt-catalyzed C–H activation

Abstract

As an earth-abundant first-row transition metal, cobalt catalysts offer a broad range of economical methods for organic transformations via C–H activation. One of the transformations is the addition of C–H to C–X multiple bonds to afford alkylation, alkenation, amidation, and cyclization products using low- or high-valent cobalt catalysts. This hydroarylation is an efficient approach to build new C–C bonds in a 100% atom-economical manner. In this review, the recent developments of Co-catalyzed hydroarylation reactions and their mechanistic studies are summarized.

Gold(I) Complexes in Ionic Liquids: An Efficient Catalytic System for the C‐H Functionalization of Arenes and Heteroarenes under Mild Conditions

“…Apart from Pd(II) and Pt(II) compounds, several other species exhibiting Lewis acid character have been considered as alternative catalysts sharing the same mechanism . Still other catalysts for this reaction are based on less electrophilic transition metal centres, which are able to undergo arene metallation followed by alkyne coordination, insertion into the metal–arene bond and final protonolysis of the resulting metal‐vinyl intermediate. The activity of these catalytic systems is however quite low, they generally require directing groups at the aromatic ring and the stereoselectivity of the reaction is not well controlled.…”

Ligand Effects in Pd-Catalyzed Intermolecular Alkyne Hydroarylations

“…Alternatively, the catalyst can first metalate the arene and subsequently insert the alkyne into the metal–aryl bond (in syn fashion); subsequent protonolysis of the intermediate regenerates the catalyst and produces the reaction product as the E stereoisomer (Scheme , at the bottom). This second possibility is generally limited to arenes featuring directing groups (which can precoordinate to the catalyst directing and promoting its attack to a specific position of the arene), , or to intramolecular reactions (in which the alkyne tethered to the arene may itself act as a directing group and insert in a second moment into the metal–aryl bond) …”

Co/Cu Co‐Catalyzed Carbonylation of Alkyl Iodides and Thioesters

“…Concerning our continue interest in carbonylation reaction and the abundant of non-nobel metal catalysts, in this work we wish to reported a cobalt/copper cocatalyzed thio-carbonylation of alkyl halides using S-alkyl butanethioate as an odorless thiol surrogate. [32][33][34][35][36] Initially, we chose iodocyclohexane and methyl thiobutyrate as model substrates to establish this carbonylation procedure. Upon variation of reaction conditions, different product yields could be obtained (Table 1).…”