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6. Construction of Vicinal Stereocenters via Asymmetric Cyanosilylation.

Author

Huang, Zhongxing

Subjects
*ALUMINUM catalysts, *KINETIC resolution, *BIOCHEMICAL substrates, *CYANOHYDRINS, *CATALYSTS
Abstract

Asymmetric cyanosilylation serves as an important tool to convert easily available ketones into cyanohydrins of diverse reactivity. Whereas a large library of organocatalysts and transition-metal catalysts have been identified for monoketones, cyanosilylation of more-complex substrates, particularly those giving enantioenriched vicinal stereocenters, is underexplored in comparison. Here, a pair of recently published kinetic resolution and desymmetrization methods are highlighted for their success in constructing complex vicinal stereocenters by cyanosilylation using tailored aluminum and magnesium catalysts, respectively. 1 Introduction 2 Kinetic Resolution of α-Branched Ketones 3 Desymmetrization of 1,3-Diketones 4 Conclusion [ABSTRACT FROM AUTHOR]

Published
2024
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17. Registration of ‘YT 09‐13’ sugarcane

Author

Wang, Qinnan, primary, Chen, Junlv, additional, Hu, Houxiang, additional, Fu, Cheng, additional, Huang, Zhongxing, additional, Zhou, Feng, additional, Qiu, Yongsheng, additional, Zhang, Chuiming, additional, Chang, Hailong, additional, and Liu, Shaomou, additional

Published
2021
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18. Total synthesis of bryostatin 3

Author

Trost, Barry M., primary, Wang, Youliang, additional, Buckl, Andreas K., additional, Huang, Zhongxing, additional, Nguyen, Minh H., additional, and Kuzmina, Olesya, additional

Published
2020
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21. Palladium-catalyzed direct β-arylation of ketones with diaryliodonium salts: a stoichiometric heavy metal-free and user-friendly approach† †Electronic supplementary information (ESI) available. CCDC 1058344–1058346. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c5sc01636c

Author

Huang, Zhongxing, Sam, Quynh P., and Dong, Guangbin

Subjects
Chemistry
Abstract

A user-friendly protocol for the Pd-catalyzed direct β-arylation of ketones is described, which avoids the use of stoichiometric heavy metals., We herein report a new protocol for the Pd-catalyzed β-arylation of ketones without stoichiometric heavy metals. Widely accessible diaryliodonium salts are used as both the oxidant and aryl source. This tandem redox catalysis merges ketone dehydrogenation and conjugate addition without an additional oxidant or reductant. This transformation features the use of a unique bis-N-tosylsulfilimine ligand and the combination of potassium trifluoroacetate/trifluoroacetic acid to maintain an appropriate acidity of the reaction medium. The reaction tolerates both air and moisture, and shows a broad substrate scope. Kinetics studies, along with filtration and poisoning tests, support the involvement of palladium nanoparticles in the catalysis.

Published
2015

22. Variations in soil bacterial communities and putative functions in a sugarcane soil following five years of chemical fertilization.

Author

Wu, Qihua, Li, Shuang, Huang, Zhongxing, and Wang, Qing

Subjects
BACTERIAL communities, POTASSIUM fertilizers, SOILS, SUGARCANE, SOIL microbiology, FERTILIZERS
Abstract

Chemical fertilizers are often applied to increase soil nutrient contents and improve crop yields. However, the impact of chemical fertilizers on abiotic and biotic characteristics of soil is unclear. Here, we investigated the variations in soil chemical properties and bacterial communities of sugarcane soil after a five-year chemical fertilization period with five different regimes, namely, Control (no fertilizer), PK (phosphorus plus potassium fertilizer), NK (nitrogen plus potassium fertilizer), NP (nitrogen plus potassium fertilizer), and NPK (combined nitrogen, phosphorus plus potassium fertilizer). We found that N-addition fertilizer treatments resulted in lower bacterial biodiversity as estimated by Chao1 and Shannon's indexes. Proteobacteria, Acidobacteria, Chloroflexi, and Actinobacteria were the predominant phyla in all of the fertilizer treatments. The concentrations of different N forms (TN, NH4+-N, and NO3–N) were the most important factors in shaping bacterial community structure. Functional groups involved in carbon, nitrogen, and sulfur cycling significantly increased or decreased with chemical N-related fertilizer treatments (NK, NP, and NPK). The community composition and functions related to element cycling of soil bacteria were strongly affected by N-containing fertilizer treatments. The results suggest that bacterial communities in sugarcane soil may have been phylogenetically and functionally altered in response to chemical fertilization. [ABSTRACT FROM AUTHOR]

Published
2021
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23. Palladium-Catalyzed β-C−H Functionalization of Ketones and Amines

Author

Huang, Zhongxing

Subjects
Organic chemistry
Abstract

A direct β-arylation reaction of simple ketones with aryl iodides is developed by merging palladium-catalyzed ketone dehydrogenation, aryl-halide activation, and conjugate addition into a single catalytic cycle. Simple cyclic ketones with different ring-sizes, as well as acyclic ketones, can be directly arylated at the β-position with complete site-selectivity and excellent functional group tolerance. In addition, the β-arylation of simple ketones was also achieved using diaryliodonium salts as the aryl source. The analysis of the redox property of the reaction indicated the β-arylation reaction does not require additional oxidant or reductant, and thus redox-neutral. The new reaction tolerates both air and moisture showing a broad substrate scope for both the ketone and aryl groups. Further exploration and improvement of the β-arylation reaction were also executed. Preliminary results regarding reaction discovery and mechanistic studies were discussed. In addition, a new hydrazone-based exo-directing group strategy is devised for the functionalization of unactivated β-C–H bonds of aliphatic amines. Protected primary amines can be readily converted to hydrazone substrates via a sequence of electrophilic amination and condensation with aldehydes. The hydrazone directing groups are shown to site-selectively promote the β-acetoxylation and -tosyloxylation via 5-membered exo-palladacycles. Amines with a wide scope of skeletons, including several pharmaceuticals, as well as a large collection of functional groups are tolerated. Moreover, the hydrazone directing groups can be readily removed, and a one-pot C–H acetoxylation/directing group removal protocol was also discovered.

Published
2017
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46. Auto-Tandem Catalysis: Synthesis of Acridines by Pd-Catalyzed C=C Bond Formation and C( sp2)-N Cross-Coupling.

Author

Huang, Zhongxing, Yang, Yang, Xiao, Qing, Zhang, Yan, and Wang, Jianbo

Abstract

A facile palladium-catalyzed synthesis of acridines has been realized by consecutive C=C double bond formation and C-N cross-coupling. A variety of functionalized acridines can be accessed from easily available o-dihalobenzenes and N-tosylhydrazones in a single operation. This one-pot protocol has a wide scope with respect to both coupling partners, and provides an efficient route to functionalized acridine derivatives, which are generally difficult to synthesize by previously known methods. [ABSTRACT FROM AUTHOR]

Published
2012
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47. Palladium-Catalyzed β-C−H Functionalization of Ketones and Amines

Author

Huang, Zhongxing

Abstract

A direct β-arylation reaction of simple ketones with aryl iodides is developed by merging palladium-catalyzed ketone dehydrogenation, aryl-halide activation, and conjugate addition into a single catalytic cycle. Simple cyclic ketones with different ring-sizes, as well as acyclic ketones, can be directly arylated at the β-position with complete site-selectivity and excellent functional group tolerance. In addition, the β-arylation of simple ketones was also achieved using diaryliodonium salts as the aryl source. The analysis of the redox property of the reaction indicated the β-arylation reaction does not require additional oxidant or reductant, and thus redox-neutral. The new reaction tolerates both air and moisture showing a broad substrate scope for both the ketone and aryl groups. Further exploration and improvement of the β-arylation reaction were also executed. Preliminary results regarding reaction discovery and mechanistic studies were discussed. In addition, a new hydrazone-based exo-directing group strategy is devised for the functionalization of unactivated β-C–H bonds of aliphatic amines. Protected primary amines can be readily converted to hydrazone substrates via a sequence of electrophilic amination and condensation with aldehydes. The hydrazone directing groups are shown to site-selectively promote the β-acetoxylation and -tosyloxylation via 5-membered exo-palladacycles. Amines with a wide scope of skeletons, including several pharmaceuticals, as well as a large collection of functional groups are tolerated. Moreover, the hydrazone directing groups can be readily removed, and a one-pot C–H acetoxylation/directing group removal protocol was also discovered.

Published
2019

50. Copper-Catalyzed Enantioselective C1,N-Dipolar (3+2) Cycloadditions of 2-Aminoallyl Cations with Indoles.

Author

Shen L, Zheng Y, Lin Z, Qin T, Huang Z, and Zi W

Abstract

2-Aminoallyl cations are versatile 1,3-dipoles that could potentially be used for diverse (3+n) cycloaddition reactions. Despite some preliminary studies, the asymmetric catalytic transformation of these species is still underdeveloped. We herein report a binuclear copper-catalyzed generation of 2-aminoallyl cations from ethynyl methylene cyclic carbamates and their enantioselective (3+2) cycloaddition reaction with indoles to construct chiral pyrroloindolines. This transformation features a novel C1,N-dipolar reactivity for 2-aminoallyl cations., (© 2022 Wiley-VCH GmbH.)

Published
2023
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