A New Class of Modular P,N‐Ligand Library for Asymmetric Pd‐Catalyzed Allylic Substitution Reactions: A Study of the Key Pd–π‐Allyl Intermediates |
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Authors: | Javier Mazuela Alexander Paptchikhine Päivi Tolstoy Oscar Pàmies Dr. Montserrat Diéguez Dr. Pher G. Andersson Prof. |
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Affiliation: | 1. Departament de Química Física i Inorgànica, Universitat Rovira i Virgili, C/Marcel líDomingo, s/n. 43007 Tarragona (Spain), Fax: (+34)?977559563;2. Department of Biochemistry and Organic Chemistry, Uppsala University, BOX 576, 751 23 Uppsala (Sweden), Fax: (+46)?18‐471‐3818 |
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Abstract: | A new class of modular P,N‐ligand library has been synthesized and screened in the Pd‐catalyzed allylic substitution reactions of several substrate types. These series of ligands can be prepared efficiently from easily accessible hydroxyl–oxazole/thiazole derivatives. Their modular nature enables the bridge length, the substituents at the heterocyclic ring and in the alkyl backbone chain, the configuration of the ligand backbone, and the substituents/configurations in the biaryl phosphite moiety to be easily and systematically varied. By carefully selecting the ligand components, therefore, high regio‐ and enantioselectivities (ee values up to 96 %) and good activities are achieved in a broad range of mono‐, di‐, and trisubstituted linear hindered and unhindered substrates and cyclic substrates. The NMR spectroscopic and DFT studies on the Pd–π‐allyl intermediates provide a deeper understanding of the effect of ligand parameters on the origin of enantioselectivity. |
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Keywords: | allylic substitution asymmetric catalysis ligand design N,P ligands palladium |
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