Fengfeng Guo

Highly enantioselective Henry reactions in water catalyzed by a copper tertiary amine complex and applied in the synthesis of (S)-N-trans-feruloyl octopamine.

Water, known as a safe, harmless, cheap, and environmentally benign solvent, has attracted continuous attention in the field of organic synthesis. In addition to the potential advantages of replacing organic solvents, water shows special properties as the reaction medium. Synthetic aqueous chemistry may help us to understand details of some biological phenomena. g] Development of aqueous asymmetric reactions could avoid tedious procedures of removing water from reactions carried out in organic solvents. Moreover, some special substrates, such as compounds commercially available as aqueous solutions or proton-containing compounds, may react smoothly in aqueous media. Many challenges remain in catalytic asymmetric C C bond formation in water, especially for asymmetric transition-metal catalysis, although considerable progress has been made in this area. Enantioselective Henry reactions have been extensively studied since 1992 due to the importance of C C bond formation. Although several Lewis acid complexes and organocatalysts have exhibited high activities and stereoselectivities for these transformations, successful examples in water are quite limited. Recently, the bifunctional guanidine–thiourea catalyst was reported in a biphasic system of water and toluene in which the corresponding products were obtained in good yields and enantiomeric excess (ee). Enzymatic catalysis has been employed for Henry reactions. These reactions were catalyzed by hydroxynitrile lyase in a biphasic aqueous system and the desired products were obtained with moderate yields and ee values. Despite these impressive contributions, reports on the use of aldehydes as substrates are limited and the enantioselectivities still need to be improved. Therefore, the development of new, more efficient, and environmentally benign catalysts for the aforementioned reaction in water is still desired and challenging. We have been focusing on investigating aqueous organic reactions. The asymmetric reaction in water is one of our main aims. Previously, we have reported an asymmetric Henry reaction catalyzed by copper Schiff base 1. Herein, we developed a highly enantioselective Lewis acid catalyzed nitroaldol reaction with water as the solvent. Excellent yields (99%) and ee values (99 %) were achieved for a wide range of aldehydes. Considering the broad application of proline derivates in aqueous aldol reactions 6] and based on ligand 1, we designed proline derivates 2 a–2 c, which were used in the asymmetric Henry reaction in water (Scheme 1). With ligands 2 a–2 c in hand, the addition of nitromethane 4 to benzaldehyde 3 a in water was chosen as a model reaction. Initially, copper acetate was employed as the Lewis acid to coordinate in situ with ligands 2 a, 2 b, and 2 c and afford the corresponding catalysts. As shown in Table 1, ligand 2 c was prominent in providing nitroalcohol 5 a in 51 % yield and [a] G. Lai, F. Guo, Y. Zheng, Y. Fang, H. Song, K. Xu, Dr. S. Wang, Dr. Z. Zha, Prof. Dr. Z. Wang Hefei National Laboratory for Physical Sciences at Microscale CAS Key Laboratory of Soft Matter Chemistry and Department of Chemistry University of Science and Technology of China, Hefei Anhui, 230026 (P.R. China) Fax: (+86) 551-3603185 E-mail : zgzha@ustc.edu.cn zwang3@ustc.edu.cn Supporting information for this article is available on the WWW under http://dx.doi.org/10.1002/chem.201002915. Scheme 1. Structures of the ligands used in this study. Bn =benzyl.

Regioselective Oxyalkylation of Vinylarenes Catalyzed by Diatomite-Supported Manganese Oxide Nanoparticles

A regioselective oxyalkylation reaction of vinylarenes with cyclic ethers was developed under the catalysis of a new heterogeneous catalyst, the diatomite-supported Mn(3)O(4) nanoparticles (SMONP-1). The use of this heterogeneous catalyst provided a novel approach for the synthesis of α-carbonyled β-alkylated aryl derivatives via a sp(3) C-H bond functionalization under mild aerobic conditions.

Copper-catalyzed enantioselective Friedel-Crafts alkylation of pyrrole with isatins.

The highly enantioselective Friedel-Crafts alkylation of pyrrole with isatins catalyzed by the tridentate Schiff base/Cu catalyst was developed. Hexafluoroisopropanol (HFIP) was used as a crucial additive to improve the enantioselectivity. In the case of N-unprotected isatins, an innovative substrate slow-releasing strategy was applied by virtue of a Henry/retro-Henry reaction.

Copper-catalyzed enantioselective hetero-Diels-Alder reaction of Danishefsky's diene with β,γ-unsaturated α-ketoesters.

A highly enantioselective hetero-Diels-Alder reaction of Danishefskys diene with β,γ-unsaturated α-ketoesters was developed for the first time by virtue of chiral copper complexes. This protocol provided a facile access to optically active dihydropyranones bearing a quaternary center with high enantioselectivities and good yields. Furthermore, on the basis of the isolated intermediate analysis, the reaction pathway was substrate-dependent.

Enantioselective Copper(I/II)‐Catalyzed Conjugate Addition of Nitro Esters to β,γ‐Unsaturated α‐Ketoesters

A highly enantioselective Michael addition of nitroacetates to β,γ-unsaturated α-ketoesters was developed by using chiral copper catalysts. The Michael addition products can be obtained in high yields with up to 99 % ee. With these densely functionalized products, the chiral cyclic nitrones, which are important synthetic intermediates, can be obtained in one step.

Metal-free synthesis of polysubstituted oxazoles via a decarboxylative cyclization from primary α-amino acids

BackgroundThe ubiquitous oxazoles have attracted more and more attention in both industrial and academic fields for decades. This interest arises from the fact that a variety of natural and synthetic compounds which contain the oxazole substructure exhibit significant biological activities and antiviral properties. Although various synthetic methodologies for synthesis of oxazols have been reported, the development of milder and more general procedure to access oxazoles is still desirable.ResultsIn this manuscript, a novel method for synthesis of polysubstituted oxazoles was developed from metal-free decarboxylative cyclization of easily available primary α-amino acids with 2-bromoacetophenones.ConclusionsThe method was simple, and this reaction could be carried out smoothly under mild and metal-free conditions. By virtue of this method, various polysubstituted oxazoles were obtained from the primary α-amino acids with moderate yields.