pi-Acidic alkene ligand effects in Pd-catalysed cross-coupling processes: exploiting the interaction of dibenzylidene acetone (dba) and related ligands with Pd(0) and Pd(II).
pi-Acidic alkene (olefin) ligands positively influence Pd-catalysed cross-coupling processes, interacting with both palladium(0) and palladium(ii) species, in some cases stabilising key catalytic intermediates. Rates of oxidative addition and reductive elimination are both affected. In certain cases, beta-hydrogen elimination can be slowed down by pi-acidic alkenes, which opens up new reaction pathways (e.g. interception of sigma-alkylpalladium(ii) species by appropriate nucleophiles). pi-Acidic alkene ligands can act independently or in a synergistic fashion with another two-electron donor ligand (e.g. amine, phosphine or N-heterocyclic carbene). The purpose of this perspective article is to highlight the impressive results that can be obtained using pi-acidic alkene ligands, with a particular focus on dibenzylidene acetone (dba) derivatives. Other types of alkene ligands, e.g. macrocyclic alkenes, are also discussed.
Fairlamb
Ian J S
IJ
Department of Chemistry, University of York, York, United Kingdom. ijsf1@york.ac.uk
D000096:Acetone / Q000737:chemistry*; D000475:Alkenes / Q000737:chemistry*; D002384:Catalysis; D008024:Ligands; D010084:Oxidation-Reduction; D010165:Palladium / Q000737:chemistry*; D010422:Pentanones / Q000737:chemistry*
D000475:Alkenes; D008024:Ligands; D010422:Pentanones; D000096:Acetone; D010165:Palladium; C533260:dibenzylidene acetone