Mechanism Tsuji–Trost reaction

first, palladium coordinates alkene, forming η2 π-allyl-pd0 Π complex. next step oxidative addition in leaving group expelled inversion of configuration , η3 π-allyl-pdii created (also called ionization). nucleophile adds allyl group regenerating η2 π-allyl-pd0 complex. @ completion of reaction, palladium detaches alkene , can start again in catalytic cycle.

hard vs. soft nucleophiles

the nucleophiles used typically generated precursors (pronucleophiles) in situ after deprotonation base. these nucleophiles subdivided hard , soft nucleophiles using paradigm describing nucleophiles largely rests on pkas of conjugate acids. hard nucleophiles typically have conjugate acids pkas greater 25, while soft nucleophiles typically have conjugate acids pkas less 25. descriptor important because of impact these nucleophiles have on stereoselectivity of product. stabilized or soft nucleophiles invert stereochemistry of π-allyl complex. inversion in conjunction inversion in stereochemistry associated oxidative addition of palladium yields net retention of stereochemistry. unstabilized or hard nucleophiles, on other hand, retain stereochemistry of π-allyl complex, resulting in net inversion of stereochemistry.

this trend explained examining mechanisms of nucleophilic attack. soft nucleophiles attack carbon of allyl group, while hard nucleophiles attack metal center, followed reductive elimination.

phosphine ligands

phosphine ligands, such triphenylphosphine or trost ligand, have been used expand scope of tsuji–trost reaction. these ligands can modulate properties of palladium catalyst such steric bulk electronic properties. importantly, these ligands can instill chirality final product, making possible these reactions carried out asymmetrically shown below.