Tienan Jin

Nanoporous Gold Catalyst for Highly Selective Semihydrogenation of Alkynes: Remarkable Effect of Amine Additives

We report for the first time the highly selective semihydrogenation of alkynes using the unsupported nanoporous gold (AuNPore) as a catalyst and organosilanes with water as a hydrogen source. Under the optimized reaction conditions, the present semihydrogenation of various terminal- and internal-alkynes affords the corresponding alkenes in high chemical yields and excellent Z-selectivity without any over-reduced alkanes. The use of DMF as solvent, which generates amines in situ, or pyridine as an additive is crucial to suppress the association of hydrogen atoms on AuNPore to form H(2) gas, which is unable to reduce alkynes on the unsupported gold catalysts. The AuNPore catalyst can be readily recovered and reused without any loss of catalytic activity. In addition, the SEM and TEM characterization of nanoporosity show that the AuNPore catalyst has a bicontinuous 3D structure and a high density of atomic steps and kinks on ligament surfaces, which should be one of the important origins of catalytic activity.

Gold-catalyzed synthesis of polycyclic enones from carbon tethered 1,3-enynyl carbonyls via tandem heteroenyne metathesis and Nazarov reaction.

An efficient and general Au(III)-catalyzed tandem reaction, heteroenyne metathesis and Nazarov cyclization, of 1,3-enynyl ketones to produce fused tri- and tetracyclic enones has been developed. The products were formed with excellent regioselectivity of the double bond position and with very high diastereoselectivities. In this reaction, the Au(III) catalyst exhibits dual roles for activating both alkynes and carbonyls.

Metal‐Catalyzed Annulation Reactions for π‐Conjugated Polycycles

The progress of the metal-catalyzed annulation reactions toward construction of various π-conjugated polycyclic cores with high conjugation extension is described. This article gives a brief overview of various annulation reactions promoted by metal catalysts including C-H bond functionalization, [2+2+2] cycloaddition, cascade processes, ring closing metathesis, electrophilic aromatization, and various cross-coupling reactions. A variety of conjugated polycycles with planar, bowl-shaped, and helical structures have been constructed in high efficiency and selectivity.

Remarkable Catalytic Property of Nanoporous Gold on Activation of Diborons for Direct Diboration of Alkynes

A novel catalytic property of nanoporous gold for activation of bis(pinacolato)diboron has been reported that allows the direct diboration of alkynes to proceed sufficiently in a heterogeneous process. The experimental results revealed that the nanoporous gold catalyst is able to cleave the B-B bond of bis(pinacolato)diboron without using any additives.

Click Chemistry of Alkyne-Azide Cycloaddition using Nanostructured Copper Catalysts

With increasing advances on nanotechnology, the nanostructured copper catalysts have attracted much attention in alkyne–azide click reaction in the last few years owing to their large surface area, tunable morphology and sustainable catalytic activities. Supported copper nanoparticles are most widely employed. The shape, size and dispersity of supported copper nanoparticles are highly controlled by the used supports, as these will determine the catalytic activity of the heterogeneous click reaction. On the other hand, nanoporous coppers with specific three‐dimensional open pore network structure was reported most recently, which can be fabricated with a tunable ligament or pore size without any supports, exhibiting high catalytic activity and reusability. This Minireview describes the state of the art with respect to the fabrication and catalytic application of both supported copper nanoparticles and nanoporous copper in click reaction.

Unsupported Nanoporous Gold Catalyst for Highly Selective Hydrogenation of Quinolines

For the first time, the highly efficient and regioselective hydrogenation of quinoline derivatives to 1,2,3,4-tetrahydroquinolines using unsupported nanoporous gold (AuNPore) as a catalyst and organosilane with water as a hydrogen source is reported. The AuNPore catalyst can be readily recovered and reused without any loss of catalytic activity.

Pd-Catalyzed Cascade Crossover Annulation of o-Alkynylarylhalides and Diarylacetylenes Leading to Dibenzo[a,e]pentalenes

A novel and selective Pd-catalyzed cascade crossover-annulation of o-alkynylarylhalides and diarylacetylenes for the synthesis of dibenzo[a,e]pentalenes has been reported. Various arylacetylenes with a wide range of functional groups were tolerated, producing the corresponding multisubstituted dibenzopentalenes with the different substituents on the aromatic rings in good to high yields under the optimized reaction conditions. The reaction proceeds through a Pd-catalyzed cascade carbopalladation and C-H activation. The use of the combined DBU and CsOPiv bases is crucial for the successful implementation of the present cross-annulation.

Highly Efficient Cu(OAc)2‐Catalyzed Dimerization of Monofunctionalized Hydrofullerenes Leading to Single‐Bonded [60]Fullerene Dimers

The single-bonded fullerene dimer RC60 C60R, which has a direct covalent bond between two C60 cages, is an interesting and unusual structure that is expected to display interesting optical and electronic properties through the interaction of two adjacent fullerene cages. Since the pioneering work by Krusic and co-workers, studies on ESR and X-ray crystalstructure analysis revealed that singly bonded fullerene dimers consist of racemic and meso isomers, which are in equilibrium with the monomer radical (RC60C) in solution. [3]

Regiospecific synthesis of 2-allyl-1,2,3-triazoles by palladium-catalyzed 1,3-dipolar cycloaddition

2-Allyl-1,2,3-triazoles were prepared by the palladium-catalyzed three component coupling (TCC) reaction of alkynes, allyl methyl carbonate and trimethylsilyl azide. A π-allylpalladium azide complex, which undergoes the 1,3-dipolar cycloaddition with alkynes, is proposed as a key intermediate in the TCC reaction.

Cobalt-catalyzed hydroalkylation of [60]fullerene with active alkyl bromides: selective synthesis of monoalkylated fullerenes.

The Co-catalyzed hydroalkylation of C(60) with reactive alkyl bromides 1 (RBr) in the presence of Mn reductant and H(2)O at ambient temperature gave the monoalkylated C(60) (2) in good to high yields. The use of CoLn/Mn/H(2)O under Ar atmosphere is crucial for the success of the present transformation. The reaction most probably proceeds through the Co(0 or I) complex-promoted generation of a radical (R(•)) followed by addition to C(60). This hydroalkylation method was applied to the synthesis of zinc porphyrin attached C(60) (2l), dendrimer attached C(60) (2m), and fullerene dimer (2n), which were not easily available through the previously known methods.