The Asymmetric Aza-Claisen Rearrangement: Development of Widely Applicable Pentaphenylferrocenyl Palladacycle Catalysts
作者:Daniel F. Fischer、Assem Barakat、Zhuo-qun Xin、Matthias E. Weiss、René Peters
DOI:10.1002/chem.200900712
日期:2009.9.7
has a broader substrate tolerance than all previously known catalyst systems for asymmetric aza‐Claisen rearrangements. Our investigations also reveal that subtle changes can have a big impact on the activity. With the enhanced catalyst activity, the asymmetric aza‐Claisen rearrangement has a very broad scope: the methodology not only allows the formation of highly enantioenriched primary allylic amines
Rhodium-Catalyzed Asymmetric 1,4-Addition of Sodium Tetraarylborates to β,β-Disubstituted α,β-Unsaturated Esters
作者:Ryo Shintani、Tamio Hayashi
DOI:10.1021/ol102674z
日期:2011.1.21
A rhodium-catalyzed1,4-addition of sodium tetraarylborates to β,β-disubstitutedα,β-unsaturated esters has been developed. Highly efficient asymmetric catalysis has also been described to create quaternary carbon stereocenters at the β-position of esters by tuning the ester group of substrates and employing a readily available chiral diene ligand.
A succinct and efficient protocol was developed for the synthesis of chiral aromatic ketones via asymmetric hydrogenation of β,β-disubstitutedenones with rhodium catalysts based on chiral bisphosphine thiourea ligands. A series of substrates (17 examples) was smoothly catalyzed to afford the corresponding chiral aromatic ketones in high conversions(>99%)with excellent enantioselectivities (up to 96%
Reactions of vinylsilanes with lewis acid-activated iodosylbenzene: stereospecific syntheses of vinyliodonium tetrafluoroborates and their reactions as highly activated vinyl halides
salts behave like the highly activated species of vinyl iodides due to the high leaving ability of the iodine(III) substituents. Thus, a variety of substituted olefins including α-cyano and α-nitro olefins, vinyl sulfides, vinyl halides, and α,β-unsaturated esters, were synthesized from under mild conditions. A ligand coupling mechanism via the formation of 10-I-3 intermediate containing a copper(III)
α,β-Unsaturated esters and amides were rapidly and selectively reduced to the corresponding saturated ones under mild conditions without affecting coexisting isolated double or triple bonds by using the reduction system, SmI2-N,N-dimethylacetamide (DMA)-proton source.