Development of spirocyclic phosphoramidite-based hybrid diphosphorus ligands for enantioselective iridium-catalyzed hydrogenation of imines.

Unsymmetrical hybrid chiral diphosphorus ligands bearing a spirocyclic phosphoramidite scaffold have been developed and successfully applied in the iridium-catalyzed asymmetric hydrogenation of imines. With this newly developed chiral iridium catalytic system, a wide range of imines including sterically hindered ones could be hydrogenated to give the corresponding optically active amines in high yields (up to >99%) and with excellent enantioselectivities (up to >99% ee). The utility of this hydrogenation has been demonstrated by the preparation of the chiral fungicide (S)-benalaxyl.

Highly Diastereo- and Enantioselective Ir-Catalyzed Hydrogenation of 2,3-Disubstituted Quinolines with Structurally Fine-Tuned Phosphine-Phosphoramidite Ligands.

A highly diastereo- and enantioselective Ir-catalyzed hydrogenation of unfunctionalized 2,3-disubstituted quinolines, especially 3-alkyl-2-arylquinolines, has been realized. The success of this hydrogenation is ascribed to the use of a structurally fine-tuned chiral phosphine-phosphoramidite ligand with a (Sa)-3,3'-dimethyl H8-naphthyl moiety and (Rc)-1-phenylethylamine backbone. The hydrogenation displayed broad functional group tolerance, thus furnishing a wide range of optically active 2,3-disubstituted tetrahydroquinolines in up to 96% ee and with perfect cis-diastereoselectivity.

Highly diastereo- and enantioselective copper-catalyzed propargylic alkylation of acyclic ketone enamines for the construction of two vicinal stereocenters.

The first highly diastereo- and enantioselective propargylic alkylation of acyclic ketone enamines to form vicinal tertiary stereocenters has been reported by employing copper catalysis in combination with a bulky and structurally rigid tridentate ketimine P,N,N-ligand.

Highly enantioselective copper-catalyzed propargylic substitution of propargylic acetates with 1,3-dicarbonyl compounds.

A chiral tridentate ketimine P,N,N-ligand has been successfully applied in the copper-catalyzed enantioselective propargylic substitution of propargylic acetates with a variety of ß-dicarbonyl compounds, in which excellent enantioselectivities (up to >99% ee) and high yields have been obtained.

Enantioselective copper-catalyzed decarboxylative propargylic alkylation of propargyl ß-ketoesters with a chiral ketimine P,N,N-ligand.

The first enantioselective copper-catalyzed decarboxylative propargylic alkylation has been developed. Treatment of propargyl ß-ketoesters with a catalyst, prepared in situ from [Cu(CH3 CN)4 BF4 ] and a newly developed chiral tridentate ketimine P,N,N-ligand under mild reaction conditions, generates ß-ethynyl ketones in good yields and with high enantioselectivities without requiring the pregeneration of ketone enolates. This new process provides facile access to a range of chiral ß-ethynyl ketones in a highly enantioenriched form.

Highly diastereo- and enantioselective Cu-catalyzed [3 + 3] cycloaddition of propargyl esters with cyclic enamines toward chiral bicyclo[n.3.1] frameworks.

A new Cu-catalyzed asymmetric [3 + 3] cycloaddition of propargyl esters with cyclic enamines is reported. With a combination of Cu(OAc)(2)·H(2)O and a chiral tridentate ferrocenyl-P,N,N ligand as the catalyst, perfect endo selectivities (endo/exo > 98/2) and excellent enantioselectivities (up to 98% ee) for endo cycloadducts were achieved under mild conditions. This method provides a simple and efficient approach for the synthesis of optically active bicyclo[n.3.1] frameworks.

Preparation and characterization of an ultrathin carbon shell coating a silver core for shell-isolated nanoparticle-enhanced Raman spectroscopy.

A well-designed type of ultrathin carbon shell coating a silver core was prepared for the first time through an alternate adsorption and carbonization method. The obtained ultrathin carbon shell shows prominent advantages, including sufficient uniformity, better chemical stability than silica or alumina, biocompatibility, being free of pin-holes and low cost.