C2-symmetric tetrahydrobis(oxazoles) are related to a class of chiral semicorrin ligands and show great promise as ligands for formation of chiral catalysts. Copper complexes of methylene-bridged bis(oxazoles) are highly efficient catalysts for enantioselective cyclopropanations, iridium complexes of directly linked bis(oxazoles) are enantioselective catalysts for transfer hydrogenations, and palladium complexes of the directly linked ligands catalyze asymmetric allylic alkylations.
D. Muller, G. Unbricht, B. Weber, A. Pfaltz, "C2-Symmetric 4,41,5,51-tetrahydro-21-methylenebis[oxazoles] as chiral ligands for enantioselective catalysis," Helvetica Chimica Acta, 74 (1), 232-38, 1991. (University of Basel, Switzerland)
Two recent papers illustrate how remote binding sites in substrates can coordinate to transition metal catalysts and alter reactions. In the first, a remote alkene controls the direction of a palladium hydride elimination. In the second, a remote alkyne delivers a palladium catalyst to a hindered allylic acetate that was otherwise completely unreactive.
B.M. Trost, M. Lautens, C. Chan, D.J. Jebaratnam, T. Mueller, "Annulation via...
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