Transition-metal mediated asymmetric synthesis. IV. Chelation of malonate esters by a chiral lanthanide shift reagent: a general method to measure theenantiomeric excess of tricarbonyl(cyclohexadienyl)iron(1+) salts

1982 ◽  
Vol 35 (9) ◽  
pp. 1939 ◽  
Author(s):  
GR Stephenson
Keyword(s):  
Transition Metal ◽  
Asymmetric Synthesis ◽  
Enantiomeric Excess ◽  
Shift Reagent ◽  
Lanthanide Shift Reagent ◽  
Derivatives Of ◽  
General Method

Chelation of dimethylmalonate derivatives of variously substituted tricarbonyl(cyclohexadienyl)-iron(1+) salts by tris(3-trifluoroacetyl-(+)-camphorato)europium(III) successfully resolved the methoxy resonances due to the two epimers of the cyclohexadiene complexes in the 1H n.m.r. spectra of racemic samples. The method provides a general means to measure enantiomeric excess of tricarbonyliron complexes.

scholarly journals Engineering of Reductive Aminases for Asymmetric Synthesis of Enantiopure Rasagiline

2021 ◽  
Vol 9 ◽  
Author(s):  
Kai Zhang ◽  
Yuanzhi He ◽  
Jiawei Zhu ◽  
Qi Zhang ◽  
Luyao Tang ◽  
...  
Keyword(s):  
Transition Metal ◽  
Chemical Synthesis ◽  
Asymmetric Synthesis ◽  
Rational Design ◽  
Enantiomeric Excess ◽  
Industrial Applications ◽  
Viable Alternative ◽  
Environmentally Benign ◽  
Secondary Amines ◽  
Metal Catalyzed

Reductive aminases (RedAms) for the stereoselective amination of ketones represent an environmentally benign and economically viable alternative to transition metal–catalyzed asymmetric chemical synthesis. Here, we report two RedAms from Aspergillus calidoustus (AcRedAm) and bacteria (BaRedAm) with NADPH-dependent features. The enzymes can synthesize a set of secondary amines using a broad range of ketone and amine substrates with up to 97% conversion. To synthesize the pharmaceutical ingredient (R)-rasagiline, we engineered AcRedAm through rational design to obtain highly stereoselective mutants. The best mutant Q237A from AcRedAm could synthesize (R)-rasagiline with >99% enantiomeric excess with moderate conversion. The features of AcRedAm and BaRedAm highlight their potential for further study and expand the biocatalytic toolbox for industrial applications.

NMR Studies of Drugs. Application of a Chiral Lanthanide Shift Reagent for Potential Direct Determination of Enantiomeric Excess of Methsuximide

1991 ◽  
Vol 24 (10) ◽  
pp. 1373-1394 ◽  
Author(s):  
Robert J. Reifsneider ◽  
Bernard H. Hoffman ◽  
Kunisi S. Venkatasubban ◽  
Robert Rothchild ◽  
Rolf Martin
Keyword(s):  
Enantiomeric Excess ◽  
Direct Determination ◽  
Shift Reagent ◽  
Lanthanide Shift Reagent ◽  
Nmr Studies

A general method towards transition metal monoboride nanopowders

2017 ◽  
Vol 108 (4) ◽  
pp. 335-338 ◽  
Author(s):  
Weixiao Cao ◽  
Ya'nan Wei ◽  
Xin Meng ◽  
Yuexia Ji ◽  
Songlin Ran
Keyword(s):  
Transition Metal ◽  
General Method

Asymmetric synthesis to chiral organosilicon compounds via transition metal-catalyzed stereoselective C-H activation and silylation

2021 ◽  
Author(s):  
Ming Zhang ◽  
Shan Gao ◽  
Juan Tang ◽  
Ling Chen ◽  
Aihua Liu ◽  
...  
Keyword(s):  
Transition Metal ◽  
Asymmetric Synthesis ◽  
Organosilicon Compounds ◽  
Feature Article ◽  
Transition Metal Catalyzed ◽  
Metal Catalyzed

This feature article introduces the progress of transition metal-catalyzed stereoselective sp2 and sp3 C-H activation and silylation to synthesize chiral organosilicon compounds, the asymmetric C-H silylation includes intramolecular cyclizing silylation...

scholarly journals The Exchange of Cyclometalated Ligands

Molecules ◽  
2021 ◽  
Vol 26 (1) ◽  
pp. 210
Author(s):  
Alexander D. Ryabov
Keyword(s):  
Transition Metal ◽  
Metal Complexes ◽  
Transition Metal Complexes ◽  
Bond Activation ◽  
Bond Cleavage ◽  
Cyclopalladated Complexes ◽  
Derivatives Of ◽  
Cyclometalated Ligand ◽  
Incoming Ligand

Reactions of cyclometalated compounds are numerous. This account is focused on one of such reactions, the exchange of cyclometalated ligands, a reaction between a cyclometalated compound and an incoming ligand that replaces a previously cyclometalated ligand to form a new metalacycle: + H-C*~Z ⇄ + H-C~Y. Originally discovered for PdII complexes with Y/Z = N, P, S, the exchange appeared to be a mechanistically challenging, simple, and convenient routine for the synthesis of cyclopalladated complexes. Over four decades it was expanded to cyclometalated derivatives of platinum, ruthenium, manganese, rhodium, and iridium. The exchange, which is also questionably referred to as transcyclometalation, offers attractive synthetic possibilities and assists in disclosing key mechanistic pathways associated with the C–H bond activation by transition metal complexes and C–M bond cleavage. Both synthetic and mechanistic aspects of the exchange are reviewed and discussed.

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