Xinming Li

Catalysis by Pd nanoclusters generated in situ of high-efficiency synthesis of aromatic azo compounds from nitroaromatics under H2 atmosphere

A facile and efficient catalytic system based on Pd nanoclusters generated in situ from Pd(acac)2 was developed for the synthesis of various aromatic azo compounds (AAzos) by hydrogenation of the corresponding nitroaromatics, using H2 as the sole reductant, under mild reaction conditions.

Highly efficient synthesis of azos catalyzed by the common metal copper (0) through oxidative coupling reactions

A facile and efficient approach to synthesize symmetric, asymmetric and bridged aromatic azo compounds (AAzos) from aromatic amines was developed by using red copper as catalyst. Despite numerous efforts towards the catalytic synthesis of symmetric and asymmetric AAzos derivatives, most reactions present certain drawbacks inhibiting their industrial applications, such as laborious multi-step processes, harsh reaction conditions and expensive reagents. And the synthesis of bridged azos had low yields before. With the presence of ammonium bromide as co-catalyst, pyridine as a ligand and molecular dioxygen as a sole oxidative reagent, red copper, a common and abundant metal in nature, exhibited unexpected catalytic activity towards the preparation of AAzos in high yields via one-step reaction, making this catalyst an attractive candidate for industrial and synthetic applications.

The synthesis of cyclohexenone using L-proline immobilized on a silica gel catalyst by a continuous-flow approach

A facile and convenient method for the synthesis of cyclohexenone compounds was developed using an L-proline immobilized silica gel catalyst combined with a continuous-flow approach. Because of the mild reaction conditions, ease of catalyst recyclability, and product isolation, this reaction approach can potentially be used in a facile scale-up reaction or in industrial applications.

An Improved Method for the Complete Hydrogenation of Aromatic Compounds under 1 Bar H2 with Platinum Nanowires

The catalytic hydrogenation of aromatic compounds to form cyclohexane derivatives represents a challenging area of research in both the general synthetic and industrial fields of chemistry. Despite recent progress in the development of homogeneous catalysts for hydrogenolysis, the properties of heterogeneous systems are generally considered to be more favorable and benign, including their lower cost, operational simplicity, and ease of separation and recyclability. Consequently, heterogeneous catalysts have been used in a broad range of industrial applications, including the production of pharmaceuticals, agrochemicals, fine chemicals, flavors, fragrances, and dietary supplements. The complete hydrogenation of aromatic compounds using current palladium, ruthenium, and rhodium metal catalysts, however, still requires the use of dangerous reaction conditions (i.e. high H2 pressures) and highly energetic pathways (>100 8C) because of the lack of active catalysts. Industrial applications in particular require high yields, high levels of selectivity and productivity, low costs, and safety and environmentally benign processes among other technical factors. The use of well-defined metal nanostructured materials in catalytic hydrogenation processes has recently become a rapidly growing area of research, and numerous studies have been devoted to the development of efficient and selective catalysts for the hydrogenation of aromatic compounds and olefins, as well as for reactions that are not catalyzed or are poorly catalyzed by molecular species. For example, Somorjai and Yang reported the catalytic hydrogenation of pyrrole using platinum nanocrystals and found that the activity and selectivity were heavily dependent on the size and shape of the nanocrystals. A similar phenomenon was also reported by Han et al. 11] with palladium nanocrystals. Gu et al. reported the direct catalytic hydrogenation of nitroaromatic compounds with one-dimensional platinum nanowires (Pt NWs), together with the coupling of carbonyl compounds with aromatic nitro compounds or the hydrogenation of aromatic compounds under 1 MPa of initial hydrogen pressure. The development of a simple, green, and efficient method for the hydrogenation of aromatic compounds is, therefore, still of considerable interest to the chemical industry and represents a significant challenge to synthetic chemists. Herein, we report the development of a novel, efficient, convenient, and environmentally benign approach to the synthesis of cyclohexane derivatives from the corresponding aromatic compounds using platinum nanowires as a catalyst in conjunction with a Lewis acid co-catalyst (e.g. , AlCl3). Pt NWs catalysts were obtained from the acidic etching of FePt NWs under an air atmosphere. (Figure 1, Figure S1 and

Efficient and ligand free palladium catalyst for Suzuki and Heck cross-coupling reactions

A simple and efficient system for Suzuki cross-coupling reactions was developed using a ligandless catalyst of Pd nanoclusters generated in situ from Pd(acac)2. The cross-coupling reactions proceeded under mild reaction conditions with a high reaction rate (5 min) to give various biaryls in high yields. The system also exhibited catalytic potential for Heck reaction between aryl bromides and styrene.

Novel transition bimetal–organic frameworks: recyclable catalyst for the oxidative coupling of primary amines to imines at mild conditions

A novel type of transition bimetal–organic frameworks was described as a heterogeneous catalyst for the oxidative coupling of amines to imines under mild conditions, which was easily synthesized by the coordination assembly of manganese(II) and cobalt(II) with 1,3,5-benzenetricarboxylic acid (H3BTC) for the first time. The metal–organic framework material was characterized by scanning electron microscopy, energy dispersive spectroscopy, X-ray photoelectron spectroscopy, X-ray diffraction, thermogravimetry and N2 sorption. As an environmentally benign heterogeneous catalyst, the catalytic ability of the metal–organic framework material was then detected to be excellent for the tert-butyl hydroperoxide (TBHP) promoted direct oxidative coupling of benzylamines to imines in excellent yields (up to 100%) in methanol for 3 h. More importantly, it could be recycled up to six runs, while still maintaining its high catalytic activity.

Synthesis of in-situ surfactant-free Pd nanoparticle catalysts for the synthesis of aromatic azo compounds and for unsaturated bond hydrogenation by hydrogen transfer

Abstract We developed a simple and efficient method to synthesize aromatic azos by hydrogen transfer using palladium(II) acetylacetonate as a catalyst and isopropyl alcohol as a hydrogen source. Furthermore, this system also showed catalytic potential for the hydrogenation of carbonyl groups or C=C bonds with yields up to ∼97%.

Understanding the Atomic-scale Process of Catalytic Assembly of Si Nanowires through Al Injection

The fabrication of self-assembled semiconductor nanowires, in particular Si nanowires, is of great interest for the development of effective and versatile nanotechnological building blocks for applications in nanoelectronics and optoelectronics. In this process, metal-catalyzed vapor-phase epitaxy is a unique synthesis method capable of generating high aspect ratio Si nanowires through the condensation of Si atoms released from a molecular vapor (Si precursor) at the surface of metallic nanoscale clusters (Figure 1). Although working as the most