Asymmetric Syntheses of Enantioenriched 2,5-Disubstituted Pyrrolidines.

-Symmetrical scaffolds are privileged ligands in metal catalysis and are also widely used in organocatalysis. Among these, 2,5-disubstituted pyrrolidines hold a paramount importance, especially since they also find application in medicinal chemistry. This review highlights the stereoselective syntheses of these -symmetrical nitrogen heterocycles.

Synthesis and crystal structure of [( )-(2-phenyl-ferrocen-yl)meth-yl]tri-methyl-ammonium iodide di-chloro-methane monosolvate.

As a follow-up to our research on the chemistry of disubstituted ferrocene derivatives, the synthesis and the structure of the title compound, [Fe(CH)(CHN)]I·CHCl, is described. The cation mol-ecule is built up from a ferrocene disubstituted by a tri-methyl-ammonium methyl group and a phenyl ring. The asymmetric unit contains the iodide to equilibrate the charge and a disordered di-chloro-methane solvate.

Oxidation-promoted activation of a ferrocene C-H bond by a rhodium complex.

The oxidation of a rhodium(I) complex containing a ferrocene-based heterodifunctional phosphine N-heterocyclic carbene (NHC) ligand produces a stable, planar chiral rhodium(III) complex with an unexpected C-H activation on ferrocene. The oxidation of rhodium(I) to rhodium(III) may be accomplished by initial oxidation of ferrocene to ferrocenium and subsequent electron transfer from rhodium to ferrocenium. Preliminary catalytic tests showed that the rhodium(III) complex is active for the Grignard-type arylation of 4-nitrobenzaldehyde via C-H activation of 2-phenylpyridine.

One-pot cross-metathesis/tandem carbonyl ylide formation-intramolecular cycloaddition of an unsaturated 2-diazo-3,6-diketoester.

Dicarbonyl-stabilised diazo functionality is tolerated during alkene cross-metathesis using Grubbs' catalyst, but undergoes subsequent tandem carbonyl ylide formation-intramolecular 1,3-dipolar cycloaddition on addition of catalytic Rh2(OAc)4 in a one-pot operation.

Catalytic enantioselective intermolecular cycloadditions of 2-diazo-3,6-diketoester-derived carbonyl ylides with alkene dipolarophiles.

Catalyzed cascade reactions that generate molecular complexity rapidly and in an enantioselective manner are attractive methods for asymmetric synthesis. In the present article, chiral rhodium catalysts are shown to effect such a transformation by using a range of 2-diazo-3,6-diketoesters with bicyclo[2.2.

The scope of catalytic enantioselective tandem carbonyl ylide formation-intramolecular [3 + 2] cycloadditions.

Catalytic enantioselective tandem carbonyl ylide formation-intramolecular 1,3-dipolar cycloaddition reactions of 2-diazo-3,6-diketoesters show promising scope in terms of asymmetric induction as the tethered alkene/alkyne dipolarophile component is varied. Cycloadditions were found to occur in moderate to very good yields, with a difference in ee exhibited by the electronically different 2-diazo-3,6-diketoesters 1, 25 and 33, 34. Values for ee of up to 90% for alkene dipolarophiles and up to 86% for alkyne dipolarophiles were obtained.

Supramolecular gold nanoparticles for the redox recognition of oxoanions: syntheses, titrations, stereoelectronic effects, and selectivity.

Stable, CH(2)Cl(2)-soluble mixed dodecanethiol/(amidoferrocenyl)alkanethiol (AFAT) gold colloids were synthesized by ligand substitution reactions from Brust's dodecanethiol gold colloids and the AFAT ligands to study the recognition and titration of oxoanions. Gold colloids were obtained with various chain lengths (C(11) and C(6) chains) of the AFAT ligand and different proportions of AFAT ligands in the colloids. Modification of the amidoferrocenyl structure [replacement of the free C(5)H(5) ferrocene ring by C(5)Me(5) (Cp) or C(5)H(4)COCH(3)] has been achieved to investigate the stereoelectronic effects on the recognition.