2010/12/23 by Jonatan Kleimark, Charlotte Johansson, Susanne Olsson +4 · 1 voice
Chemistry · #Asymmetric Hydrogenation and Catalysis #Asymmetric Synthesis and Catalysis #Catalytic C–H Functionalization Methods
paper · doi:10.1021/om1007264
The selectivity in the Pd-assisted allylic alkylation has been investigated in a system with a ligand tethered to the allylic moiety. Isolation of (η 3 -allyl)Pd complexes and stoichiometric reaction with malonate nucleophiles allowed separation of various factors influencing the regioselectivity in a system that cannot undergo apparent rotation. Unexpectedly, trans effects were found to have only a minor influence on the selectivity, whereas changing the tether length could shift the preference from favored internal to dominant terminal attack. DFT-assisted analysis revealed that the dominant selectivity-determining factors are the forced rotation of the allylic moiety and an important steric repulsion from a syn- alkyl substituent.