Iridium Phosphite−Oxazoline Catalysts for the Highly Enantioselective Hydrogenation of Terminal Alkenes
摘要:
A modular library of readily available phosphite-oxazoline ligands (L1-L16a-f) has been successfully applied for the first time in the Ir-catalyzed asymmetric hydrogenation of a broad range of highly unfunctionalized 1,1,-disubstituted terminal alkenes. Enantioselectivities up to >99% and full conversions were obtained in several 1, 1 -disubstituted alkenes, including substrate classes that have never been asymmetrically hydrogenated before (i.e,, 1,1-heteoraryl-alkyl, 1,1-diaryl, trifluoromethyl, etc.). The results indicated that these catalytic systems have high tolerance to the steric and electronic requirements of the substrate and also to the presence of a neighboring polar group. The asymmetric hydrogenations were also performed using propylene carbonate as solvent, which allowed the It catalyst to be reused and maintained the excellent enantioselectivities.
Iridium Phosphite−Oxazoline Catalysts for the Highly Enantioselective Hydrogenation of Terminal Alkenes
作者:Javier Mazuela、J. Johan Verendel、Mercedes Coll、Benjamín Schäffner、Armin Börner、Pher G. Andersson、Oscar Pàmies、Montserrat Diéguez
DOI:10.1021/ja904152r
日期:2009.9.2
A modular library of readily available phosphite-oxazoline ligands (L1-L16a-f) has been successfully applied for the first time in the Ir-catalyzed asymmetric hydrogenation of a broad range of highly unfunctionalized 1,1,-disubstituted terminal alkenes. Enantioselectivities up to >99% and full conversions were obtained in several 1, 1 -disubstituted alkenes, including substrate classes that have never been asymmetrically hydrogenated before (i.e,, 1,1-heteoraryl-alkyl, 1,1-diaryl, trifluoromethyl, etc.). The results indicated that these catalytic systems have high tolerance to the steric and electronic requirements of the substrate and also to the presence of a neighboring polar group. The asymmetric hydrogenations were also performed using propylene carbonate as solvent, which allowed the It catalyst to be reused and maintained the excellent enantioselectivities.
Modular Phosphite–Oxazoline/Oxazine Ligand Library for Asymmetric Pd-Catalyzed Allylic Substitution Reactions: Scope and Limitations—Origin of Enantioselectivity
作者:Montserrat Diéguez、Oscar Pàmies
DOI:10.1002/chem.200701636
日期:2008.4.18
A library of phosphite-oxazoline/oxazine ligands L1-L15 a-h 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 amino acid derivatives. Their modular nature enables the substituents/configurations in the oxazoline/oxazine moiety, alkyl backbone chain and in