Chiral-Anion-Dependent Inversion of Diastereo- and Enantioselectivity in Carbonyl Crotylation via Ruthenium-Catalyzed Butadiene Hydrohydroxyalkylation

The ruthenium catalyst generated in situ from H2Ru(CO)(PPh3)(3), (S)-SEGPHOS, and a TAD-DOL-derived phosphoric acid promotes butadiene hydro-hydroxyalkylation to form enantiomerically enriched products. Notably, the observed diastereo- and enantioselectivity is the opposite of that observed using BINOL-derived phosphate counterions in combination with (S)-SEGPHOS, the same enantiomer of the chiral ligand. Match/mismatch effects between the chiral ligand and the chiral TADDOL-phosphate counterion are described. For the first time, single-crystal X-ray diffraction data for a ruthenium complex modified by a chiral phosphate counterion are reported.