Browsing by Author "Ge, Haibo"
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Item Benzisothiazol‐3‐ones through a Metal‐Free Intramolecular N–S Bond Formation(Wiley, 2018-11) Yang, Ke; Zhang, Hao; Niu, Ben; Tang, Tiandi; Ge, Haibo; Chemistry and Chemical Biology, School of ScienceThe highly efficient synthesis of benzoisothiazol‐3‐ones from thiobenzamides has been described with good functional group compatibility and excellent yields. This work represents the first example of selectfluor‐promoted N–S bond formation processes. This method provides a facile approach to access various important bioactive benzoisothiazol‐3‐ones.Item Cobalt-catalysed site-selective intra- and intermolecular dehydrogenative amination of unactivated sp3 carbons(Nature Publishing Group, 2015-03-10) Wu, Xuesong; Yang, Ke; Zhao, Yan; Sun, Hao; Li, Guigen; Ge, Haibo; Department of Chemistry & Chemical Biology, School of ScienceCobalt-catalysed sp2 C–H bond functionalization has attracted considerable attention in recent years because of the low cost of cobalt complexes and interesting modes of action in the process. In comparison, much less efforts have been devoted to the sp3 carbons. Here we report the cobalt-catalysed site-selective dehydrogenative cyclization of aliphatic amides via a C–H bond functionalization process on unactivated sp3 carbons with the assistance of a bidentate directing group. This method provides a straightforward synthesis of monocyclic and spiro β- or γ-lactams with good to excellent stereoselectivity and functional group tolerance. In addition, a new procedure has been developed to selectively remove the directing group, which enables the synthesis of free β- or γ-lactam compounds. Furthermore, the first cobalt-catalysed intermolecular dehydrogenative amination of unactivated sp3 carbons is also realized., Functionalizing unactivated carbon–hydrogen bonds is challenging, especially when using non-precious metals and dealing with sp3 hybridized carbons. Here, the authors report an intramolecular cobalt catalysed amination of C–H bonds of sp3 carbons, giving access to β- and γ-lactams.Item A Computational Study of the Mechanism for F1-ATPase Inhibition by the Epsilon Subunit(2013) Thomson, Karen J.; Pu, Jingzhi; Ge, Haibo; Sardar, Rajesh; Long, Eric C. (Eric Charles)The multi-protein complex of F0F1 ATP synthase has been of great interest in the fields of microbiology and biochemistry, due to the ubiquitous use of ATP as a biological energy source. Efforts to better understand this complex have been made through structural determination of segments based on NMR and crystallographic data. Some experiments have provided useful data, while others have brought up more questions, especially when structures and functions are compared between bacteria and species with chloroplasts or mitochondria. The epsilon subunit is thought to play a signi cant role in the regulation of ATP synthesis and hydrolysis, yet the exact pathway is unknown due to the experimental difficulty in obtaining data along the transition pathway. Given starting and end point protein crystal structures, the transition pathway of the epsilon subunit was examined through computer simulation.The purpose of this investigation is to determine the likelihood of one such proposed mechanism for the involvement of the epsilon subunit in ATP regulation in bacterial species such as E. coli.Item Copper-catalyzed diastereoselective aerobic intramolecular dehydrogenative coupling of hydrazones via sp3 C–H functionalization(Royal Society of Chemistry, 2015) Wu, Xuesong; Wang, Mian; Zhang, Guangwu; Zhao, Yan; Wang, Jianyi; Ge, Haibo; Department of Chemistry & Chemical Biology, School of ScienceTransition metal-catalyzed cross dehydrogenative coupling is an important tool for functionalization of the α Csp3–H bond of amines. Among this reaction category, copper-catalyzed selective C–C bond formation under atmospheric O2 is of considerable research interest and significant progress has been achieved in recent years. In comparison, development of the intramolecular version of this transformation is still in its infancy. Furthermore, diastereoselective cyclization with this transformation has not been achieved. Here, we describe the highly diastereoselective intramolecular dehydrogenative cyclization of N,N-disubstituted hydrazones by a copper-catalyzed sp3 C–H bond functionalization process. The reaction protocol utilizes O2 as the oxidant and shows great functional group compatibility. Computational studies suggest that a 5-center/6-electron disrotatory cyclization mechanism is probably involved in the process for controlling the diastereoselectivity. This work represents the first example of a copper-catalyzed, direct intramolecular diastereoselective coupling reaction via an iminium ion intermediate. Additionally, it provides an environmentally friendly and atom efficient approach to access substituted pyrazolines, an important structural unit in many biologically active compounds.Item Copper-promoted site-selective carbonylation of sp3 and sp2 C–H bonds with nitromethane(RSC, 2016-08) Wu, Xuesong; Miao, Jinmin; Li, Yanrong; Li, Guigen; Ge, Haibo; Department of Chemistry & Chemical Biology, School of ScienceCopper-promoted direct carbonylation of unactivated sp3 C–H and aromatic sp2 C–H bonds of amides was developed using nitromethane as a novel carbonyl source. The sp3 C–H functionalization showed high site-selectivity by favoring the C–H bonds of α-methyl groups. The sp2 C–H carbonylation featured high regioselectivity and good functional group compatibility. Kinetic isotope effect studies indicated that the sp3 C–H bond breaking step is reversible, whereas the sp2 C–H bond cleavage is an irreversible but not the rate-determining step. Control experiments showed that a nitromethyl intermediate should be involved in the present reaction.Item Direct Aerobic Carbonylation of C(sp2)-H and C(sp3)-H Bonds through Ni/Cu Synergistic Catalysis with DMF as the CO Source(ACS, 2015-03) Wu, Xuesong; Zhao, Yan; Ge, Haibo; Department of Chemistry & Chemical Biology, IU School of ScienceThe direct carbonylation of aromatic sp2 and unactivated sp3 C–H bonds of amides was achieved via nickel/copper catalysis under atmospheric O2 with the assistance of a bidentate directing group. The sp2 C–H functionalization showed high regioselectivity and good functional group compatibility. The sp3 C–H functionalization showed high site-selectivity by favoring the C–H bonds of α-methyl groups over those of the α-methylene, β- or γ-methyl groups. Moreover, this reaction showed a predominant preference for functionalizing the α-methyl over α-phenyl group. Mechanistic studies revealed that nickel/copper synergistic catalysis is involved in this process.Item Dual hepatocyte-targeting fluorescent probe with high sensitivity to tumorous pH: Precise detection of hepatocellular carcinoma cells(Elsevier, 2019-04) Zhang, Yamin; Li, Zhenjie; Ge, Haibo; Zhu, Xueyan; Zhao, Zhuang; Qi, Zhong-quan; Wang, Mian; Wang, Jianyi; Chemistry and Chemical Biology, School of ScienceA new dual hepatocyte-targeting fluorescent probe HPL-1, which can precisely distinguish tumorous pH from physiological pH, was developed. The OFF-ON switch of HPL-1 can be triggered via pH-induced structural change of the lactam group of the rhodamine moiety from closed-ring to open-ring. Our results showed that the phosphate group of HPL-1 is beneficial to its accumulation in liver cells, and combination of the phosphate and galactose units could synergistically increase the hepatocyte-targeting capacity. HPL-1 could selectively distinguish hepatoma cells from other tissue cells, and precisely distinguish cancerous liver cells from normal liver cells. Compared with other reported probes, HPL-1 not only enable a simple and convenient detection method, but also has good hepatocyte-targeting capacity and precise recognition capacity of tumors under weak acid micro-environment, which opens new avenues for precise diagnosis and treatment of hepatocellular carcinoma.Item Highly selective electrochemical hydrogenation of alkynes: Rapid construction of mechanochromic materials(American Association for the Advancement of Science, 2019-05-24) Li, Bijin; Ge, Haibo; Chemistry and Chemical Biology, School of ScienceElectrochemical hydrogenation has emerged as an environmentally benign and operationally simple alternative to traditional catalytic reduction of organic compounds. Here, we have disclosed for the first time the electrochemical hydrogenation of alkynes to a library of synthetically important Z-alkenes under mild conditions with great selectivity and efficiency. The deuterium and control experiments of electrochemical hydrogenation suggest that the hydrogen source comes from the solvent, supporting electrolyte, and base. The scanning electron microscopy and x-ray diffraction experiments demonstrate that palladium nanoparticles generated in the electrochemical reaction act as a chemisorbed hydrogen carrier. Moreover, complete reduction of alkynes to saturated alkanes can be achieved through slightly modified conditions. Furthermore, a series of novel mechanofluorochromic materials have been efficiently constructed with this protocol that showed blue-shifted mechanochromism. This discovery represents the first example of cis-olefins-based organic mechanochromic materials.Item The modification of brucine derivatives as chiral ligands and its application in the asymmetric synthesis(2014) Li, Jian-yuan; Minto, Robert; Ge, Haibo; Abu-Omar, Mahdi; Wilker, Jonathan; Long, Eric C. (Eric Charles)The modification of brucine derivatives as chiral ligands and the use of a multifaceted chiral ligand, brucine diol, under different reaction conditions to produce various optical isomers is described. In Chapter 1, the generation of a number of brucine derivatives is described. Taking the advantage of brucine-diol’s excellent molecular recognition capability for multiple organic functional groups, we focused on the synthetic modifications of brucine-diol and the synthesis of brucine N-oxide. We also produced various brucine derivatives with different functional moieties in good yields and selectivities. In Chapter 2, we described the investigation of brucine N-oxide catalyzed Morita-Baylis-Hillman (MBH) reaction of alkyl/aryl ketones. Brucine N-oxide was used as a nucleophilic organic catalyst in the MBH reaction of alkyl vinyl ketone. In addition, asymmetric MBH reactions of alkyl vinyl ketones with aldehydes were investigated using a dual catalysis of brucine N-oxide and proline. In this dual catalyst system, proline was found to form iminium intermediates with electron-deficient aryl aldehydes, while the N-oxide activated vinyl ketones provided enolates through the conjugate addition. Our dual catalysis approach also allowed the development of MBH reaction of aryl vinyl ketones. In Chapter 3, brucine diol-copper complex catalyzed asymmetric conjugate addition of glycine (ket)imines to nitroalkenes is discussed. Stereodivergent catalytic asymmetric conjugate reactions for glycine (ket)imines with nitroalkenes were achieved using various chiral catalysts derived from a single chiral source, brucine diol. Both syn- and anti-conjugate addition products were obtained with high diastereoselectivity and enantioselectivity. In Chapter 4, enantiodivergent production of endo-pyrrolidines from glycine (ket)imines using brucine diol-copper complex is described. The [3+2] cycloaddition reaction of glycine imines and activated alkenes was performed to produce endo-pyrrolidines. The reversal of enantioselectivity was observed for endo-pyrrolidines between concerted and stepwise reaction pathways. The three new brucine derivatives produced in this study would potentially work as organocatalysts and chiral ligands with metal ion in asymmetric synthesis. The brucine diol-metal complex catalyzed reactions laid a good foundation for catalytic asymmetric reactions, where a single chiral source was used to control the absolute and the relative stereochemical outcomes of reactions. Understanding the molecular-level interactions between catalyst and substrates will provide insightful mechanistic details for the stereodivergent approaches in asymmetric catalysis.Item Palladium-Catalyzed Decarboxylative Alkoxycarbonylation of Potassium Aryltrifluoroborates with Potassium Oxalate Monoesters(RSC, 2016-02) Miao, Jinmin; Fang, Ping; Jagdeep, Sahota; Ge, Haibo; Department of Chemistry and Chemical Biology, School of SciencePalladium-catalyzed decarboxylative alkoxycarbonylation of potassium aryltrifluoroborates with potassium oxalate monoesters in the presence of potassium persulfate was performed under mild conditions. A number of benzoyl esters with a wide variety of substituents at different positions were efficiently synthesized with this method. Mechanism of the palladium-catalyzed decarboxylative carbonylation of aryltrifluoroborates was studied, and a radical-mediated Pd(II)/Pd(IV) catalytic cycle was proposed.