Ligands In Asymmetric Metal Catalysis Research Articles

Chiral organophosphates as ligands in asymmetric metal catalysis

Chiral phosphates have successfully been used as ligands in asymmetric metal-catalysis. This Minireview discusses the most recent examples, including main-group catalysis, transition-metal catalysis and catalysis by rare-earth metals.

Rhodium-Catalyzed Regio- and Enantioselective Allylic Amination of Racemic 1,2-Disubstituted Allylic Phosphates.

Alkynylphosphines are rarely used as ligands in asymmetric metal catalysis. We synthesized a series of chiral bis(oxazoline)alkynylphosphine ligands and used them in Rh-catalyzed highly regio- and enantioselective allylic amination reactions of 1,2-disubstituted allylic phosphates. Chiral 1,2-disubstituted allylic amines were synthesized in up to 95% yield with >20:1 branched/linear (b/l) ratio and 99% ee from racemic 1,2-disubstituted allylic precursors. The sterically smaller linear alkynyl group on the P atom in the bis(oxazoline)alkynylphosphine ligands was the key to fit the new requirements of the introduction of bulky 2-R' groups.

Designing successful monodentate N-heterocyclic carbene ligands for asymmetric metal catalysis.

Chiral ligands are of particular importance in asymmetric transition-metal catalysis. Although the development of effective chiral monodentate N-heterocyclic carbenes (NHCs) has been slow, a growing amount of papers have been published in recent years showing their unique efficiency as chiral ancillary ligands. Herein we provide an overview of NHC structures that accomplish high levels of enantioselectivity (≥90% ee) and give guidelines to their use and thoughts on the future of this field.

ChemInform Abstract: Design of Supramolecular Chiral Ligands for Asymmetric Metal Catalysis

AbstractReview: [38 refs.

ChemInform Abstract: Synthesis of Phosphorylated Sulfoximines and Sulfinamides and Their Application as Ligands in Asymmetric Metal Catalysis.

AbstractSeveral sulfoximine‐ and sulfinamide‐based phosphorusamides are prepared from inexpensive and easily available educts.

Synthesis of phosphorylated sulfoximines and sulfinamides and their application as ligands in asymmetric metal catalysis

Starting from inexpensive materials and following simple protocols various N-phosphorylated sulfoximines and sulfinamides have been synthesized. The newly prepared compounds were then applied as chiral ligands in asymmetric transition metal catalysis. Phosphorus triamide-type ligands derived from ( S)-glutamic acid were found to be the most efficient stereoselectors in enantioselective palladium-catalyzed allylic substitutions (up to 97% ee). On the other hand, diamidophosphite-type structures stemming from ( S)-proline were the best ligands in rhodium-catalyzed hydrogenation reactions (up to 84% ee).

Synthesis of Chiral Sulfonimidamides and Application in Asymmetric Henry Reaction

Sulfonimidamides, the aza-analogues of sulfonamides, have been of interests as chiral nitrene precursors and due to their bioactivities. However, their application as chiral ligands in asymmetric metal catalysis has not yet been fully explored. The authors have developed two synthetic routes for the synthesis of enantiopure ­amino-functionalized sulfonimidamides 4 from readily available materials. These compounds have been successfully employed as chiral ligands in asymmetric copper-catalyzed Henry reactions to afford good yields and up to 95% ee.

ChemInform Abstract: Catalytic Asymmetric Synthesis: Chemical Methods. Sulfoximines as Ligands in Asymmetric Metal Catalysis

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Preparation of new chiral borane-protected P,N-ferrocenyl ligands via a methoxy directedortho-lithiation

We have shown that the readily prepared (ferrocenyl)benzylic methyl ethers of type 1 can be ortho-metalated with tert-BuLi with high diastereoselectivity. This reaction has been used to prepare new borane-protected P,N-substituted ferrocenes of type 2 in high diastereomeric and enantiomeric purity. The chiral heterocyclic aminophosphines 2 may be of interest as chelating ligands for asymmetric metal catalysis.

ChemInform Abstract: New Non‐C2‐Symmetric Phosphine‐Phosphonites as Ligands in Asymmetric Metal Catalysis.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

New non- C2-symmetric phosphine-phosphonites as ligands in asymmetric metal catalysis

Starting from 1,2-dibromobenzene, the synthesis of N,N,N′, N′-tetraethyl-[2-(diphenylphosphino)phenyl]phosphonous acid tetraamide is possible in two simple steps. This key compound reacts with a variety of chiral diols such as ( R)- and ( S)-binaphthol, 1,2:5,6-diisopropylidene- d-mannitol or (1 R,2 R)-1,2-diphenyl-1,2-ethane diol to form the corresponding non- C 2-symmetric phosphine-phosphonite compounds. These ligands react with Rh(COD) 2BF 4 to form bidentate Rh-complexes which serve as catalysts in the asymmetric hydrogenation of dimethyl itaconate with ee values of up to 88%.