A novel method for the synthesis of π-conjugated phosphindolium salts via copper-mediated C-H functionalization of trisubstituted phosphines with alkynes in a single step is reported. The reactions are highly regioselective with unsymmetrical aryl-alkyl-substituted alkynes. This protocol provides an unprecedented atom- and step-efficient access to valuable phosphindolium salts.

The direct carboxylation of inert aryl C−H bond catalyzed by abundant and cheap nickel is still facing challenge. Herein, we report the Ni‐catalyzed direct carboxylation of aryl C−H bonds in benzamides under 1 atm of CO2 to afford various methyl carboxylates or phthalimides, dealing with different post‐processing. The reaction displays excellent functional group tolerance and affords moderate to high carboxylation yields under mild conditions. Detail mechanistic studies suggest that a Ni(0)−Ni(II)−Ni(I) catalytic cycle may be involved in this reaction.

The transition-metal-catalyzed direct carboxylation of an unactivated C–H bond is rarely reported, and no example of catalysis using abundant and cheap nickel has been reported. In this work, the first Ni-catalyzed direct carboxylation of an unactivated C–H bond under an atmospheric pressure of CO2 is reported. This method affords moderate to high carboxylation yields of various methyl carboxylates under mild conditions. Preliminary mechanistic studies reveal that a Ni(0)–Ni­(II)–Ni­(I) catalytic cycle may be involved in this reaction.

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