Activation of Aryl Carboxylic Acids by Diboron Reagents towards Nickel-Catalyzed Direct Decarbonylative Borylation

The Ni-catalyzed decarbonylative borylation of (hetero)aryl carboxylic acids with B(2)cat(2) has been achieved without recourse to any additives. This Ni-catalyzed method exhibits a broad substrate scope covering poorly reactive non-ortho-substituted (hetero)aryl carboxylic acids, and tolerates diverse functional groups including some of the groups active to Ni-0 catalysts. The key to achieve this decarbonylative borylation reaction is the choice of B(2)cat(2) as a coupling partner that not only acts as a borylating reagent, but also chemoselectively activates aryl carboxylic acids towards oxidative addition of their C(acyl)-O bond to Ni-0 catalyst via the formation of acyloxyboron compounds. A combination of experimental and computational studies reveals a detailed plausible mechanism for this reaction system, which involves a hitherto unknown concerted decarbonylation and reductive elimination step that generates the aryl boronic ester product. This mode of boron-promoted carboxylic acid activation is also applicable to other types of reactions.

Automated summary

The Ni-catalyzed decarbonylative borylation of (hetero)aryl carboxylic acids with B(2)cat(2) has been achieved without additives, covering a broad substrate scope and tolerating diverse functional groups. Experimental and computational studies revealed a detailed mechanism involving a concerted decarbonylation and reductive elimination step.