| Abstract
| - The structural 3,5-dialkylphenyl effect on enantioselectivity is demonstrated for several Pd-catalyzed reactions including a ring-opening transmetalation, Heck arylation, and allylic alkylation. Detailed NMR and X-ray data are reported. The principle has been expanded to a monodentate phosphine, MOP.
- The structural 3,5-dialkylphenyl effect on enantioselectivity is demonstrated for severalPd-catalyzed reactions including a ring-opening transmetalation, Heck arylation, and allylicalkylation. For these homogeneously catalyzed reactions the observed enantiomeric excesses(ee's) are found to improve by more than 15%. The ligands tested include MeO-Biphep anda P,N-phosphino-oxazoline-bidentate ligand containing 3,5-di-tert-butylphenyl substituents.Further, several derivatives of the monodentate auxiliary MOP ((R)-2-diarylphosphino-1,1‘-binaphthyl) have been modified to include 3,5-dialkylphenyl substituents and theseauxiliaries have been tested in Pd-catalyzed enantioselective hydrosilylation chemistry. Forsome, but not all of these MOP ligands, enhanced ee's of the order of 40−50% are found.Variable-temperature and 2-D NMR studies have been carried out on new model complexesand reveal selected restricted rotation around a number of the P−C(ipso) aryl bonds. Solid-state structures for two of the new complexes, PdBr(p-NCC6H4)(phosphino-oxazoline, 2b),8b, and PdCl(C6H4CH2NMe2)(MOP, 4b), 9b, have been determined.
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