Minxue Huang

Bio: Minxue Huang is an academic researcher from University of Wisconsin-Madison. The author has contributed to research in topics: Nitrene & Amination. The author has an hindex of 6, co-authored 6 publications receiving 142 citations. Previous affiliations of Minxue Huang include Nanjing Tech University.

Inverting Steric Effects: Using "Attractive" Noncovalent Interactions To Direct Silver-Catalyzed Nitrene Transfer.

Abstract: Nitrene transfer (NT) reactions represent powerful and direct methods to convert C–H bonds into amine groups that are prevalent in many commodity chemicals and pharmaceuticals. The importance of the C–N bond has stimulated the development of numerous transition-metal complexes to effect chemo-, regio-, and diastereoselective NT. An ongoing challenge is to understand how subtle interactions between catalyst and substrate influence the site-selectivity of the C–H amination event. In this work, we explore the underlying reasons why Ag(tpa)OTf (tpa = tris(pyridylmethyl)amine) prefers to activate α-conjugated C–H bonds over 3° alkyl C(sp3)–H bonds and apply these insights to reaction optimization and catalyst design. Experimental results suggest possible roles of noncovalent interactions (NCIs) in directing the NT; computational studies support the involvement of π···π and Ag···π interactions between catalyst and substrate, primarily by lowering the energy of the directed transition state and reaction conforme...

Silver-Catalyzed Enantioselective Propargylic C-H Bond Amination through Rational Ligand Design.

Abstract: Asymmetric C–H amination via nitrene transfer is a powerful tool to prepare enantioenriched amine precursors from abundant C–H bonds. Herein, we report a regio- and enantioselective synthesis of γ-...

Novel 3D lanthanide-organic frameworks with an unusual infinite nanosized ribbon [Ln3(μ3–OH)2(–CO2)6]+n (Ln = Eu, Gd, Dy): syntheses, structures, luminescence, and magnetic properties

Abstract: Three novel lanthanide-organic frameworks, [Ln3(μ3–OH)2L2(HCO2)3(H2O)2]·H2O (Ln = Eu (1), Gd (2), Dy (3); H2L = 3,3′-dimethoxy-4,4′-biphenyldicarboxylic acid), have been prepared by the solvothermal reaction of Ln(NO3)3·6H2O and H2L in DMF/H2O mixed solvent. Crystallographic data show that 1–3 are isomorphous and crystallize in the monoclinic space groupP21/c. Each complex contains a rare infinite nanosized ribbon [Ln3(μ3–OH)2(–CO2)6]+n with three crystallographically distinct Ln(III) ions: two nine-coordinated and one eight-coordinated. The nanosized ribbons are interconnected through HCO2− anions and L2− linkers to yield a 3D framework. Furthermore, 1 exhibits strong red luminescence upon 343 nm excitation. The investigation of the magnetic properties shows the weak antiferromagnetic coupling between Gd(III) ions in 2 but ferromagnetic coupling between the Dy(III) ions in 3.

Synthesis, Characterization, and Variable-Temperature NMR Studies of Silver(I) Complexes for Selective Nitrene Transfer

Abstract: An array of silver complexes supported by nitrogen-donor ligands catalyze the transformation of C═C and C–H bonds to valuable C–N bonds via nitrene transfer. The ability to achieve high chemoselectivity and site selectivity in an amination event requires an understanding of both the solid- and solution-state behavior of these catalysts. X-ray structural characterizations were helpful in determining ligand features that promote the formation of monomeric versus dimeric complexes. Variable-temperature 1H and DOSY NMR experiments were especially useful for understanding how the ligand identity influences the nuclearity, coordination number, and fluxional behavior of silver(I) complexes in solution. These insights are valuable for developing improved ligand designs.

Tunable catalyst-controlled syntheses of β- and γ-amino alcohols enabled by silver-catalysed nitrene transfer

Abstract: Carbon–hydrogen bond functionalization methods are important tools for efficiently upgrading simple precursors to more valuable compounds. The ubiquity of amines in pharmaceuticals and natural products has led to considerable interest in strategies for the selective amidation of C–H bonds in a tunable manner. An ongoing challenge involves achieving control in situations where targeted bonds have varying bond strengths or similar steric/electronic environments. Herein, we report two complementary silver catalysts that are capable of selecting between β- or γ-C–H bonds that reside in similar steric/electronic environments, overriding a reaction at a weaker C–H bond in favour of a stronger one and activating primary C–H bonds. The mild conditions, low cost of silver, good yields and easy purification make this approach ideal for late-stage functionalizations to furnish valuable 1,2- and 1,3-aminoalcohols from easily prepared carbamate esters. One of the major challenges in C–H functionalization is to achieve selectivity when multiple bonds of similar reactivity are present. Now, a method to selectively amidate sterically and electronically similar β- or γ-C–H bonds that utilize different silver catalysts is reported, giving access to valuable 1,2- and 1,3-aminoalcohols.

Development of dispersive micro-solid phase extraction based on micro and nano sorbents

Abstract: Dispersive micro-solid phase extraction (D-μ-SPE) as a new type of solid phase extraction (SPE) is attractive for a variety of analytical applications including pre-concentration, clean-up and extraction methods. A comparison of D-μ-SPE with SPE method from several analytical and economical aspects is presented. Up to now the application of D-μ-SPE for the determination of many analytes is increasing due to the simplicity, fastness and low cost of it. Another important feature of D-μ-SPE is the diversity of solid sorbents to achieve specific selectivity and high extraction efficiency. Many reports have discussed the synthesis and application of different sorbents in D-μ-SPE. With the rise of nanotechnology, a large number of synthetic nano-material is widely used to enhance the extraction efficiency and reduce the extraction time of D-μ-SPE. Most studies focused on the magnetic nanocomposites sorbents. Herein, we summarize the type of sorbents and review the latest progress in D-μ-SPE.

Tunable, Chemo- and Site-Selective Nitrene Transfer Reactions through the Rational Design of Silver(I) Catalysts

Abstract: ConspectusCarbon–nitrogen (C–N) bonds are ubiquitous in pharmaceuticals, agrochemicals, diverse bioactive natural products, and ligands for transition metal catalysts. An effective strategy for introducing a new C–N bond into a molecule is through transition metal-catalyzed nitrene transfer chemistry. In these reactions, a metal–supported nitrene can either add across a C═C bond to form an aziridine or insert into a C–H bond to furnish the corresponding amine. Typical catalysts for nitrene transfer include Rh2Ln and Ru2Ln complexes supported by bridging carboxylate and related ligands, as well as complexes based on Cu, Co, Ir, Fe, and Mn supported by porphyrins and related ligands.A limitation of metal-catalyzed nitrene transfer is the ability to predictably select which specific site will undergo amination in the presence of multiple reactive groups; thus, many reactions rely primarily on substrate control. Achieving true catalyst-control over nitrene transfer would open up exciting possibilities for fle...

Cation-π Interactions in Organic Synthesis.

Abstract: The cation−π interaction is an attractive noncovalent interaction between a cation and a π system. Due to the stronger interaction energy than those of the other π interactions, such as π–π and CH−π interactions, the cation−π interaction has recently been recognized as a new tool for controlling the regio- and stereoselectivities in various types of organic reactions. This review attempts to cover a variety of organic reactions controlled by cation−π interactions, which includes not only recent examples but also those reported before the term “cation−π interaction” was defined in 1990. This review will provide comprehensive knowledge on the role of cation−π interactions in organic synthesis.

Lanthanide Anionic Metal-Organic Frameworks Containing Semirigid Tetracarboxylate Ligands: Structure, Photoluminescence, and Magnetism

Abstract: A series of lanthanide anionic metal–organic frameworks, [NH2(CH3)2][Ln(MDIP)(H2O)] (Ln = Pr (1), Nd (2), Sm (3), Eu (4), Gd (5), Tb (6), Dy (7); H4MDIP = methylenediisophthalic acid) and [NH2(CH3)2][Ln(MDIP)(H2O)]·0.5NH(CH3)2 (Ln = Er (8), Tm (9), Yb (10)), have been synthesized and characterized. In compounds 1–7, the adjacent Ln3+ ions are intraconnected to form infinite metal-carboxylate oxygen chain-shaped building blocks along the [001] direction. In compounds 8–10, MDIP ligands bridge dinuclear lanthanide centers to form three-dimensional frameworks which can be rationalized as a (4,8)-connected topological net with the Schlafli symbol of (410.614.84)(45.6)2. Dimethylamine cations occupy the vacancy of all the compounds as counterions. The photophysical properties of trivalent Pr, Nd, Sm, Eu, Tb, Dy, Er, Yb compounds at room temperature were investigated and showed that MDIP is an efficient sensitizer of the luminescence of both the Tb3+ ion emitting visible light and the Yb3+ ion emitting in the n...