Gold-catalyzed tandem reactions of methylenecyclopropanes and vinylidenecyclopropanes.

Gold catalysis is often the key step in the synthesis of natural products, and is a powerful tool for tandem or domino reaction processes. Both gold salts and complexes are among the most powerful soft Lewis acids for electrophilic activation of carbon-carbon multiple bonds toward a variety of nucleophiles. The core of these reactions relies on the interaction between gold catalysts and π-bonds of alkenes, alkynes, and allenes.

Rhodium(I)-catalyzed cycloisomerization of nitrogen-tethered indoles and alkylidenecyclopropanes: convenient access to polycyclic indole derivatives.

At the end of its tether: A new synthetic protocol for the preparation of polycyclic indole derivatives has been developed from a rhodium(I)-catalyzed cycloisomerization of a nitrogen-tethered indole and alkylidenecyclopropane, affording the corresponding tetrahydro-β-carboline derivatives in moderate to good yields. Further transformations give a direct and rapid route to tetracyclic compounds through transition-metal catalysis.

Transition metal-catalyzed carbocyclization of nitrogen and oxygen-tethered 1,n-enynes and diynes: synthesis of five or six-membered heterocyclic compounds.

Cycloisomerization of 1,n-enynes and diynes is a powerful method in organic synthesis to access heterocyclic compounds and has drawn increasing attention from organic chemists. In this paper, we attempted to summarize our recent results on the transition metal-catalyzed cycloisomerization to synthesize five or six-membered heterocyclic compounds using 1,n-enynes and diynes having a propargylic ester moiety. First, we will describe the synthesis of 2,3-disubstituted 3-pyrrolines via gold catalyzed cycloisomerization of 1,6-diynes.

Gold(I)-catalyzed intramolecular hydroamination and ring-opening of sulfonamide-substituted 2-(arylmethylene)cyclopropylcarbinols.

An interesting gold(I)-catalyzed intramolecular hydroamination and ring-opening of sulfonamide-substituted 2-(arylmethylene)cyclopropylcarbinols has been described in this context. A variety of 4-substituted isoxazolidine derivatives were obtained in good to high yields through a highly regioselective cleavage of a carbon-carbon single bond in the cyclopropane.

[Characteristics of polycyclic aromatic hydrocarbons (PAHS) on airborne particulates in Beijing].

Total suspended particulates (TSP) samples were collected from Sep., 2003 to Jul., 2004 in Beijing, and 15 kinds of PAHs, ranging from 3 to 7 rings were analyzed.