page_title: Decarboxylative cross-coupling
section_title: Palladium-–copper bimetallic systems
hierarchical_section_title: Decarboxylative cross-coupling / History and catalyst development / Palladium-–copper bimetallic systems
caption_attribution_description: English: Biaryl synthesis using a Cu/Pd catalyst system, reported by Shang et al.png
context_page_description: Decarboxylative cross coupling reactions are chemical reactions in which a carboxylic acid is reacted with an organic halide to form a new carbon-carbon bond, concomitant with loss of CO₂. Aryl and alkyl halides participate. Metal catalyst, base, and oxidant are required.
  A significant advantage of this reaction is that it uses relatively inexpensive carboxylic acids and is far less air and moisture sensitive in comparison to typical cross-coupling organometallic reagents. Furthermore, the carboxylic acid moiety is a common feature of natural products and can also be prepared by relatively benign air oxidations. Additional benefits include the broad tolerance of functional groups, as well as the capacity to avoid the use of strong bases. An important elementary step in this reaction is protodecarboxylation or metalation to first convert the C–COOH bond to a C–H or C–M bond respectively.
context_section_description: A Pd–Cu bimetallic system was not discovered until 2006 when Goossen et al. reported a decarboxylative cross-coupling of aryl halides with ortho-substituted aromatic carboxylic acids.
  Through subsequent studies it was found that the use of aryl triflates allowed substrate scope for cross-coupling to be extended to some aromatic carboxylates lacking any ortho-substitution (less reactive). This was a result of the fact that any halide anion generated in the reaction inhibited the Cu-catalyzed decarboxylation process.
  Further optimization of the system and catalyst conditions has made decarboxylative cross-coupling using bimetallic Pd–Cu systems applicable to organic synthesis, most predominantly in the formation of biaryls.
  As well, the variability of this combined catalytic system allows for promotion of a large spectrum of reactions, including aryl ketone formation, c-heteroatom cross-coupling, and many others.
caption: Biaryl synthesis using a Cu–Pd catalyst system, reported by Shang et al.
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