Liquid-liquid biphasic systems that exhibit an increase in phase miscibilit
y at elevated temperature together with soluble polymer-bound catalysts tha
t have a strong phase preference at ambient temperature are described. In s
uch systems, product isolation and catalyst recovery are effected by a liqu
id/liquid separation. This report-describes the use of such thermomorphic c
atalyst recovery systems for palladium-catalyzed carbon-carbon bond forming
reactions. Poly(N-isopropylacrylamide) (PNIPAM)-bound phosphine ligands wi
th a Pd(0) catalyst used previously in allylic substitution chemistry are e
fficient catalysts in Heck, Suzuki, and sp-sp(2) cross-coupling reactions.
Air-stable tridentate SCS-Pd(II) catalysts bound to PNIPAM or poly(ethylene
glycol) (PEG) are also described. A particular advantage of these SCS cata
lysts is that no precautions against adventitious catalyst oxidation need b
e taken with the polymer-bound SCS-PdCl catalysts; thus avoiding time-consu
ming solvent purification and degassing protocols.