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. 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 and a P,N-phosphino-oxazoline-bidentate ligand containing 3,5-di-tert-butylphenyl substituents. Further, several derivatives of the monodentate auxiliary MOP (CR)-2-diarylphosphino-1,1′-binaphthyl) have been modified to include 3,5-dialkylphenyl substituents and these auxiliaries have been tested in Pd-catalyzed enantioselective hydrosilylation chemistry. For some, 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 complexes and reveal selected restricted rotation around a number of the P-C(ipso) aryl bonds. Solid-state structures for two of the new complexes, PdBrCp-NCCeHUXphosphino-oxazoline, 2b), 8b, and PdCl(C 6H 4CH 2NMe 2)(MOP, 4b), 9b, have been determined.
3,5-Dialkyl Effect on Enantioselectivity in Pd Chemistry: Applications Involving Both Bidentate and Monodentate Auxiliaries / P. Dotta, P. G. Anil Kumar, P. S. Pregosin, A. Albinati, S. Rizzato. - In: ORGANOMETALLICS. - ISSN 0276-7333. - 2004:12(2004), pp. 2295-2304.
|Titolo:||3,5-Dialkyl Effect on Enantioselectivity in Pd Chemistry: Applications Involving Both Bidentate and Monodentate Auxiliaries|
ALBINATI, ALBERTO (Penultimo)
RIZZATO, SILVIA (Ultimo)
|Settore Scientifico Disciplinare:||Settore CHIM/03 - Chimica Generale e Inorganica|
|Data di pubblicazione:||2004|
|Digital Object Identifier (DOI):||http://dx.doi.org/10.1021/om034381b|
|Appare nelle tipologie:||01 - Articolo su periodico|