Browsing by Author "Li, Guigen (TTU)"
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Item A new chiral phenomenon of orientational chirality, its synthetic control and computational study(2023) Jin, Shengzhou; Xu, Ting; Tang, Yao (TTU); Wang, Jia Yin; Wang, Yu; Pan, Junyi; Zhang, Sai (TTU); Yuan, Qingkai (TTU); Rahman, Anis Ur (TTU); Aquino, Adelia J.A. (TTU); Lischka, Hans (TTU); Li, Guigen (TTU)A new type of chirality, orientational chirality, consisting of a tetrahedron center and a remotely anchored blocker, has been discovered. The key structural element of this chirality is characterized by multiple orientations directed by a through-space functional group. The multi-step synthesis of orientational chiral targets was conducted by taking advantage of asymmetric nucleophilic addition, Suzuki-Miyaura cross-coupling and Sonogashira coupling. An unprecedented catalytic species showing a five-membered ring consisting of C (sp2)-Br-Pd-C (sp2) bonds was isolated during performing Suzuki-Miyaura cross-coupling. X-ray diffraction analysis confirmed the species structure and absolute configuration of chiral orientation products. Based on X-ray structures, a model was proposed for the new chirality phenomenon to differentiate the present molecular framework from previous others. DFT computational study presented the relative stability of individual orientatiomers. This discovery would be anticipated to result in a new stereochemistry branch and to have a broad impact on chemical, biomedical, and material sciences in the future.Item Aggregation-induced polarization (AIP) of derivatives of BINOL and BINAP(2022) Tang, Yao (TTU); Yuan, Qingkai (TTU); Wang, Yu; Zhang, Sai (TTU); Wang, Jia-Yin; Jin, Shengzhou; Xu, Ting; Pan, Junyi; Guilbeau, Collin Ray (TTU); Pleasant, Alyssa Jenae (TTU); Li, Guigen (TTU)The relationship between optical rotations of small chiral molecules with water% in THF has been established. The typical aggregation co-solvent systems resulted in optical rotation amplification and adjustment, defined as aggregation-induced polarization (AIP). The AIP work can serve as a new tool to determine molecular aggregation, especially for those that cannot display aggregation-induced emission (AIE). Therefore, AIP and AIE are anticipated to complement each other. In addition, AIP can also serve as a new transmission tool providing adjusting right- or left-hand polarized lights of a series of individual wavelengths. Since chiral phosphine derivatives are among the most important ligands, this work would benefit research using chiral aggregates to control asymmetric synthesis and catalysts. Therefore, it will find many applications in chemical and materials sciences.Item Aggregation-Induced Polarization (AIP): Optical Rotation Amplification and Adjustment of Chiral Aggregates of Folding Oligomers and Polymers(2022) Tang, Yao (TTU); Zhang, Sai (TTU); Xu, Ting; Yuan, Qingkai (TTU); Wang, Jia-Yin; Jin, Shengzhou; Wang, Yu; Pan, Junyi; Griffin, Isaac (TTU); Chen, Daixiang; Li, Guigen (TTU)The phenomenon of aggregation-induced polarization (AIP) was observed showing optical rotation amplification and adjustment. The relationship between optical rotations of chiral aggregates of multilayered chiral folding oligomers and polymers with water% in THF (fw) has been established accordingly. New multilayered chiral oligomers were synthesized under the asymmetric catalytic systems established by our laboratory recently. These products were well-characterized by UV-vis, NMR, and MALDI-TOF spectra. Absolute stereochemistry (enantio- and diastereochemistry) was assigned by comparison with similar asymmetric induction by the same catalyst in our previous reactions. The present AIP work can serve as a new tool to determine chiral aggregates, especially for those that cannot display emission. AIP would also complement AIE-based CPL since AIP serves as a new tool providing enhanced right- or left-hand polarized lights with individual wavelengths. It will find many applications in chemical and materials science in the future.Item C(sp)-C(sp) Lever-Based Targets of Orientational Chirality: Design and Asymmetric Synthesis(2024) Xu, Ting; Wang, Jia Yin; Wang, Yu; Jin, Shengzhou; Tang, Yao (TTU); Zhang, Sai (TTU); Yuan, Qingkai (TTU); Liu, Hao (TTU); Yan, Wenxin; Jiao, Yinchun; Yang, Xiao Liang; Li, Guigen (TTU)In this study, the design and asymmetric synthesis of a series of chiral targets of orientational chirality were conducted by taking advantage of N-sulfinylimine-assisted nucleophilic addition and modified Sonogashira catalytic coupling systems. Orientational isomers were controlled completely using alkynyl/alkynyl levers [C(sp)-C(sp) axis] with absolute configuration assignment determined by X-ray structural analysis. The key structural element of the resulting orientational chirality is uniquely characterized by remote through-space blocking. Forty examples of multi-step synthesis were performed, with modest to good yields and excellent orientational selectivity. Several chiral orientational amino targets are attached with scaffolds of natural and medicinal products, showing potential pharmaceutical and medical applications in the future.Item Catalytic arylsulfonyl radical-triggered 1,5-enyne-bicyclizations and hydrosulfonylation of α,β-conjugates(2015) Chen, Zhen Zhen; Liu, Shuai; Hao, Wen Juan; Xu, Ge; Wu, Shuo; Miao, Jiao Na; Jiang, Bo; Wang, Shu Liang; Tu, Shu Jiang; Li, Guigen (TTU)A catalytic bicyclization reaction of 1,5-enynes anchored by α,β-conjugates with arylsulfonyl radicals generated in situ from sulfonyl hydrazides has been established using TBAI (20 mol%) and Cu(OAc)2 (5 mol%) as co-catalysts under convenient conditions. In addition, the use of benzoyl peroxide (BPO) as the oxidant and pivalic acid (PivOH) as an additive was proven to be necessary for this reaction. The reactions occurred through 5-exo-dig/6-endo-trig bicyclizations and homolytic aromatic substitution (HAS) cascade mechanisms to give benzo[b]fluorens regioselectively. A similar catalytic process was developed for the synthesis of γ-ketosulfones. These reactions feature readily accessible starting materials and simple one-pot operation.Item Central-to-Folding Chirality Control: Asymmetric Synthesis of Multilayer 3D Targets With Electron-Deficient Bridges(2022) Jin, Shengzhou; Wang, Jia Ying; Tang, Yao (TTU); Rouh, Hossein (TTU); Zhang, Sai (TTU); Xu, Ting; Wang, Yu; Yuan, Qingkai (TTU); Chen, Daixiang; Unruh, Daniel (TTU); Li, Guigen (TTU)New multilayer 3D chiral molecules have been designed and synthesized asymmetrically through the strategy of center-to-multilayer folding chirality control and double Suzuki couplings. Individual diastereoisomers were readily obtained and separated via flash column chromatography. The key diastereoisomer was further converted into corresponding enantiomers. These enantiomers possess electron-deficient aromatic bridges layered with top and bottom aromatic scaffolds. X-ray structural analysis has unambiguously confirmed the configuration, and intermolecular packing results in regular planar patterns in solid crystals. The synthesis was achieved in a total of ten steps starting from commercially available starting materials.Item Cobalt-catalysed site-selective intra-and intermolecular dehydrogenative amination of unactivated sp3carbons(2015) Wu, Xuesong; Yang, Ke; Zhao, Yan; Sun, Hao; Li, Guigen (TTU); Ge, HaiboCobalt-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 sp 3 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 2-or γ 3-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 2-or γ 3-lactam compounds. Furthermore, the first cobalt-catalysed intermolecular dehydrogenative amination of unactivated sp 3 carbons is also realized.Item Copper-Catalyzed Annulation–Cyanotrifluoromethylation of 1,6-Enynes Toward 1-Indanones via a Radical Process(2020) Zhang, Tian Shu; Hao, Wen Juan; Cai, Pei Jun; Li, Guigen (TTU); Tu, Shu Jiang; Jiang, BoA new Cu(II)-catalyzed annulation–cyanotrifluoromethylation of 1,6-enynes with Togni's reagent and trimethylsilyl cyanide (TMSCN) has been established, enabling the direct construction of trifluoromethylated 1-indanones with an all-carbon quaternary center in good yields. This reaction was performed by using low-cost Cu(OTf)2 as the catalyst and Togni's reagent as both the radical initiator and a CF3 source, providing an efficient protocol for building up an 1-indanone framework with wide functional group compatibility. The reaction mechanism was proposed through a radical triggered addition/5-exo-dig cyclization/oxidation/nucleophilic cascade.Item Copper-promoted site-selective carbonylation of sp3 and sp2 C-H bonds with nitromethane(2016) Wu, Xuesong; Miao, Jinmin; Li, Yanrong; Li, Guigen (TTU); Ge, HaiboCopper-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 Double SO2 Insertion into 1,7-Diynes Leading to Functionalized Naphtho[1,2-c]thiophene 2,2-dioxides(2018) Wang, Ai Fang; Hao, Wen Juan; Zhu, Yi Long; Li, Guigen (TTU); Zhou, Peng; Tu, Shu Jiang; Jiang, BoA novel metal-free double SO2 insertion/multicomponent bicyclization cascade of benzene-linked 1,7-diynes has been established by treatment with aryldiazonium tetrafluoroborates and DABCO-bis(sulfur dioxide) under redox-neutral conditions, providing a range of dual sulfone-containing naphtho[1,2-c]thiophene 2,2-dioxides with generally high stereoselectivity. The reaction pathway is proposed to proceed through the sequence of arylsulfonyl-radical-induced 6-exo-dig/5-endo-trig bicyclization, H-abstraction, and diazotization.Item Enantioselective assembly of multi-layer 3D chirality(2020) Wu, Guanzhao (TTU); Liu, Yangxue (TTU); Yang, Zhen; Jiang, Tao; Katakam, Nandakumar (TTU); Rouh, Hossein (TTU); Ma, Liulei (TTU); Tang, Yao (TTU); Ahmed, Sultan (TTU); Rahman, Anis U.; Huang, Hongen; Unruh, Daniel (TTU); Li, Guigen (TTU)The first enantioselective assembly of sandwich-shaped organo molecules has been achieved by conducting dual asymmetric Suzuki-Miyaura couplings and nine other reactions. This work also presents the first fully C-C anchored multi-layer 3D chirality with optically pure enantiomers. As confirmed by X-ray diffraction analysis that this chiral framework is featured by a unique C2-symmetry in which a nearly parallel fashion consisting of three layers: top, middle and bottom aromatic rings. Unlike the documented planar or axial chirality, the present chirality shows its top and bottom layers restrict each other from free rotation, i.e., this multi-layer 3D chirality would not exist if either top or bottom layer is removed. Nearly all multi-layered compounds showed strong luminescence of different colors under UV irradiation, and several randomly selected samples displayed aggregation-induced emission (AIE) properties. This work is believed to have broad impacts on chemical, medicinal and material sciences including optoelectronic materials in future.Item Fe(III)-catalyzed bicyclization of yne-allenones with indoles for the atom-economic synthesis of 3-indolyl cyclobutarenes(2018) Li, Heng; Hao, Wen Juan; Li, Guigen (TTU); Tu, Shu Jiang; Jiang, BoA new Fe(III)-catalyzed bicyclization reaction of yne-allenones with indoles has been established, enabling the direct construction of cyclobuta[a]naphthalen-4-ols with an all-carbon quaternary center in good to excellent yields. This reaction was performed by using low-cost FeCl3 as the catalyst and EtOH as the environmentally benign solvent, providing a green protocol for constructing the cyclobutarene framework with a high degree of atom economy and functional group compatibility. The reaction mechanism was proposed to proceed through a [2 + 2] cycloaddition/1,6-conjugate addition cascade.Item Four-layer folding framework: design, GAP synthesis, and aggregation-induced emission(2023) Zhang, Sai (TTU); Chen, Daixiang; Wang, Jia Yin; Yan, Shenghu; Li, Guigen (TTU)The design and synthesis of a type of [1 + 4 + 2] four-layer framework have been conducted by taking advantage of Suzuki–Miyaura cross-coupling and group-assisted purification (GAP) chemistry. The optimized coupling of double-layer diboronic esters with 1-bromo-naphth-2-yl phosphine oxides resulted in a series of multilayer folding targets, showing a broad scope of substrates and moderate to excellent yields. The final products were purified using group-assisted purification chemistry/technology, achieved simply by washing crude products with 95% EtOH without the use of chromatography and recrystallization. The structures were fully characterized and assigned by performing X-ray crystallographic analysis. UV–vis absorption, photoluminescence (PL), and aggregation-induced emission (AIE) were studied for the resulting multilayer folding products.Item Group-Assisted Purification (GAP) Chemistry for the Synthesis of Velcade via Asymmetric Borylation of N-Phosphinylimines(2014) Xie, Jian Bo (TTU); Luo, Jian (TTU); Winn, Timothy R. (TTU); Cordes, David B. (TTU); Li, Guigen (TTU)A new approach to the anticancer drug Velcade was developed by performing asymmetric borylation of an imine anchored with a chiral N-phosphinyl auxiliary. Throughout the 7-step synthesis, especially in the imine's synthesis and in the asymmetric borylation reactions, operations and work-up were conducted in simple and easy ways without any column chromatographic purification, which defines the GAP (group-assisted purification) chemistry concept. It was found that the optically pure isomer (dr > 99:1) can be readily obtained by washing the crude mixture of the asymmetric borylation reaction with hexane; the chiral N-phosphinyl auxiliary can be easily recovered after deprotection is finished. Several other N-phosphinylimines were also investigated for the asymmetric borylation reaction. The absolute configuration of the borylation product was confirmed by single crystal X-ray diffraction analysis.© 2014 Xie et al.Item Hypervalent Iodine (III) Catalyzed Regio- and Diastereoselective Aminochlorination of Tailored Electron Deficient Olefins via GAP Chemistry(2020) Rahman, Anis Ur; Zarshad, Nighat; Zhou, Peng; Yang, Weitao; Li, Guigen (TTU); Ali, AsadHerein, we report a protocol for highly efficient hypervalent iodine (III) mediated, group-assisted purification (GAP) method for the regioselectivities and stereoselective aminochlorination of electron-deficient olefins. A series of vicinal chloramines with multifunctionalities were acquired in moderate to excellent yields (45–94%), by merely mixing the GAP auxiliary-anchored substrates with dichloramine T and tosylamide as chlorine/nitrogen sources and iodobenzene diacetate as a catalyst. The vicinal chloramines were obtained without any column chromatographic purification and recrystallization simply by washing the reaction mixture with a minimum amount of common inexpensive solvents and thus avoiding wastage of silica, solvents, time, and labor. The GAP auxiliary is recyclable and reusable. This strategy is easy to handle, cost-effective, greener, sustainable, environmentally benign, and mostly suitable for the syntheses of vicinal haloamines from various electron-deficient alkenes.Item New multiple-layered 3D polymers showing aggregation-induced emission and polarization(2024) Zhang, Sai; Yuan, Qingkai (TTU); Li, Guigen (TTU)An exceptional achiral and chiral multilayer 3D polymer has been created and controlled by uniform and distinct aromatic chromophore units that are multiply sandwiched by naphthyl berths. In order to put together this assembly, it was necessary to search for new catalytic Suzuki-Miyaura polycouplings among various catalytic systems, monomers, and catalysts. Gel Permeation Chromatography (GPC) was able to verify the presence of many framework layers. The resulting achiral and chiral polymers displayed notable optical characteristic.Item One-pot stereoselective synthesis of α,β-differentiated diamino esters via the sequence of aminochlorination, aziridination and intermolecular SN2 reaction(2014) Xiong, Yiwen; Qian, Ping; Cao, Chenhui; Mei, Haibo; Han, Jianlin; Li, Guigen (TTU); Pan, YiWe report here an efficient one-pot method for the synthesis of α,β-differentiated diamino esters directly from cinnamate esters using N,N-dichloro-p-toluenesulfonamide and benzylamine as nitrogen sources. The key transformations include a Cu-catalyzed aminohalogenation and aziridination, followed by an intermolecular SN2 nucleophilic ring opening by benzylamine. The reactions feature a wide scope of substrates and proceed with excellent stereo- and regioselectivity (anti:syn >99:1). © 2014 Xiong et al; licensee Beilstein-Institut.Item Photocatalytic Multicomponent Annulation of Amide-Anchored 1,7-Diynes Enabled by Deconstruction of Bromotrichloromethane(2024) Chen, Daixiang; Bao, Yu; Yan, Shenghu; Wang, Jiayin; Zhang, Yue; Li, Guigen (TTU)We present the first example of visible-light-mediated multicomponent annulation of 1,7-diynes by taking advantage of quadruple cleavage olf carbon-halogen bonds of BrCCl3 to generate a C1 synthon, which was adeptly applied to the preparation of skeletally diverse 3-benzoyl-quinolin-2(1H)-one acetates in moderate to good yields. Controlled experiments demonstrated that H2O acted as both oxygen and hydrogen sources, and gem-dichlorovinyl carbonyl compound exhibited as a critical intermediate in this process. The mechanistic pathway involves Kharasch-type addition/6-exo-dig cyclization/1,5-(SN”)-substitution/elimination/binucleophilic 1,6-addition/proton transfer/tautomerization sequence.Item Photocatalytic radical defluoroalkylation of unactivated alkenes via distal heteroaryl ipso-migration(2020) Yuan, Xin; Zhuang, Kai Qiang; Cui, Yu Sheng; Qin, Long Zhou; Sun, Qi; Duan, Xiu; Chen, Lin; Zhu, Ning; Li, Guigen (TTU); Qiu, Jiang Kai; Guo, KaiCurrently, the selective activation of C(sp3)–F bonds and C–C bonds constitute one of the most widely used procedures for the synthesis of high-value products that range from pharmaceuticals to agrochemical applications. While numerous examples of these two methods have been reported in their respective fields, the processes which merge the activation of both single C(sp3)-F bonds and C–C bonds in one step still remain elusive. Here, we demonstrate the controllable defluoroalkylation–distal functionalization of trifluoromethylarenes with unactivated alkenes via distal heteroaryl migration. This is proposed to proceed via tandem C(sp3)–F and C–C bond cleavage using visible-light photoredox catalysis combined with Lewis acid activation. This strategy provides facile and flexible access to multiply functionalized α,α-difluorobenzylic ketones in useful yields (up to 88%) under mild conditions. The products can be further transformed into other valuable compounds, demonstrating the method’s utility.Item Photoinduced radical tandem annulation of 1,7-diynes: an approach for divergent assembly of functionalized quinolin-2(1H)-ones(2024) Chen, Daixiang; Song, Zhi Jie; Yan, Shenghu; Li, Guigen (TTU); Wang, Jia Yin; Zhang, YueThe first photocatalytic trichloromethyl radical-triggered annulative reactions of amide-linked 1,7-diynes with polyhalomethanes were established for the flexible assembly of functionalized quinolin-2(1H)-ones with generally acceptable yields. With the installation of the aryl group (R1) into the alkynyl moiety, C-center radical-initiated Kharasch-type addition/nucleophilic substitution/elimination cascade to produce quinolin-2(1H)-ones-incorporating gem-dihaloalkene, whereas three examples of polyhalogenated quinolin-2(1H)-ones were afforded when amide-linked 1,7-diynes bearing two terminal alkyne units were subjected to BrCX3 by exploiting dry acetonitrile as a solvent.