Chen Li

Bio: Chen Li is an academic researcher from Zhejiang University of Technology. The author has contributed to research in topics: Enantioselective synthesis & Cascade reaction. The author has an hindex of 2, co-authored 5 publications receiving 13 citations.

Asymmetric synthesis of polysubstituted chiral chromans via an organocatalytic oxa-Michael-nitro-Michael domino reaction

Abstract: A catalytic asymmetric method for the synthesis of polysubstituted chromans via an oxa-Michael-nitro-Michael reaction has been developed. The squaramide-catalyzed domino reaction of 2-hydroxynitrostyrenes with trans-β-nitroolefins produced chiral chromans with excellent enantioselectivities (up to 99% ee), diastereoselectivities (up to >20 : 1 dr), and moderate to good yields (up to 82%).

Nitrogen-doped graphene/tungsten oxide microspheres as an electro-catalyst support for formic acid electro-oxidation

Abstract: Tungsten trioxide (WO3) spheres decorated with nitrogen-doped graphene (NRGO–WO3) were synthesized by applying the spray-drying procedure and characterized for their ability to serve as an electro-catalyst support for formic acid electro-oxidation. A possible mechanism for the formation of NRGO–WO3 was proposed based on the results of tunneling electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). Pd nanoparticles with dimensions of 4.8 nm were loaded onto the surface of NRGO–WO3 using a conventional sodium borohydride reduction method. The electrocatalytic performances of Pd/NRGO–WO3 for formic acid oxidation were investigated by using cyclic voltammetry and chronoamperometry. Due to the decrease in the resistance to electron transfer resulting from the modification of N-doped graphene, which produced an excellent electrical conductor, as well as due to the hydrogen spill-over effect, which accelerated the dehydrogenation of formic acid on Pd active sites, a great enhancement of the electrochemical performances was achieved.

One-pot asymmetric synthesis of a hexahydrophenanthridine scaffold containing five stereocenters via an organocatalytic quadruple-cascade reaction

Abstract: An organocatalytic enantioselective aza-Michael-Michael-Michael/aldol cyclization quadruple-cascade reaction of 2-amino-β-nitrostyrenes and α,β-unsaturated aldehydes has been developed for the construction of fully substituted hexahydrophenanthridine. This cascade reaction was efficiently catalyzed by diphenylprolinol TMS ether furnishing the tricyclic compounds containing hexahydrophenanthridine bearing five contiguous stereogenic centers with excellent diastereoselectivities (up to >99 : 1 dr) and high to excellent enantioselectivities (up to >99% ee). Application in the gram-scale synthesis of the tricyclic compounds containing hexahydrophenanthridine was also successfully realized.

Base-controlled chemoselectivity: direct coupling of alcohols and acetonitriles to synthesise α-alkylated arylacetonitriles or acetamides

Abstract: [Cp*IrCl2]2 with a phosphine-free ligand α,α,α-terpyridine shows high catalytic performance in chemodivergent synthesis of α-alkylated arylacetonitriles in the presence of K2CO3 and α-alkylated acetamides in the presence of tBuOK, respectively.

Direct N-alkylation of sulfur-containing amines.

Abstract: An efficient ruthenium-catalyzed method has been developed for the direct N-alkylation of sulfur-containing amines with alcohols, for the first time, by a step-economical and environmentally friendly hydrogen borrowing strategy. The present methodology features base-free conditions and broad substrate scope, with water being the only by-product. Moreover, this protocol has been applied to the synthesis of the pharmaceutical drug Quetiapine.

Xanthones from fungi, lichens, and bacteria : the natural products and their synthesis

Abstract: Many fungi, lichens, and bacteria produce xanthones (derivatives of 9H-xanthen-9-one, “xanthone” from the Greek “xanthos”, for “yellow”) as secondary metabolites. Xanthones are typically polysubstituted and occur as either fully aromatized, dihydro-, tetrahydro-, or, more rarely, hexahydro-derivatives. This family of compounds appeals to medicinal chemists because of their pronounced biological activity within a notably broad spectrum of disease states, a result of their interaction with a correspondingly diverse range of target biomolecules. This has led to the description of xanthones as “privileged structures”.(1) Historically, the total synthesis of the natural products has mostly been limited to fully aromatized targets. Syntheses of the more challenging partially saturated xanthones have less frequently been reported, although the development in recent times of novel and reliable methods for the construction of the (polysubstituted) unsaturated xanthone core holds promise for future endeavors. In particular, the fascinating structural and biological properties of xanthone dimers and heterodimers may excite the synthetic or natural product chemist.

Supercritical antisolvent coprecipitation mechanisms

Abstract: Supercritical antisolvent precipitation (SAS) has been successfully used to produce microparticles and nanoparticles of controlled size and distribution either as a single precipitates or by coprecipitation of two or more compounds. SAS coprecipitation process has produced different particles morphologies and, differently from the single compound SAS precipitation, process mechanisms involved have never been elucidated and the effectiveness of the technique has been verified only in some cases. In this work, the mechanisms proposed in SAS coprecipitation are critically discussed and general indications about coprecipitation efficiency are given, based on several experimental evidences and on the possible underlying nucleation, growth and drying mechanisms. The most effective and reliable SAS coprecipitation resulted from the formation of microdroplets and their subsequent drying.

AgPd Nanoparticles Deposited on WO2.72 Nanorods as an Efficient Catalyst for One-Pot Conversion of Nitrophenol/Nitroacetophenone into Benzoxazole/Quinazoline

Abstract: We report a seed-mediated growth of 2.3 nm AgPd nanoparticles (NPs) in the presence of 40 × 5 nm WO2.72 nanorods (NRs) for the synthesis of AgPd/WO2.72 composites. The strong interactions between AgPd NPs and WO2.72 NRs make the composites, especially the Ag48Pd52/WO2.72, catalytically active for dehydrogenation of formic acid (TOF = 1718 h–1 and Ea = 31 kJ/mol) and one-pot reactions of formic acid, 2-nitrophenol, and aldehydes into benzoxazoles in near quantitative yields under mild conditions. The catalysis can also be extended to the one-pot reactions of ammonium formate, 2-nitroacetophenone, and aldehyde for high yield syntheses of quinazolines. Our studies demonstrate a new catalyst design to achieve a green chemistry approach to one-pot reactions for the syntheses of benzoxazoles and quinazolines.

Recent advances in organocatalytic asymmetric oxa-Michael addition triggered cascade reactions

Abstract: The oxa-Michael cascade reaction, as an important part of the Michael reaction, has also been significantly developed over the recent decade. This is because the problem of the reactivity and selectivity of the addition reactions of oxygen nucleophiles to conjugated systems has been solved by different organocatalysts and reaction conditions. Therefore, using various efficient strategies, many novel and potentially bioactive chiral compounds with excellent yields and stereoselectivities have been synthesized. In this review, we summarize the recent advances in organocatalytic asymmetric oxa-Michael addition triggered cascade reactions for the stereoselective synthesis of heterocyclic compounds.