Organic Chemistry Commons^™

Kinetic Resolution Of Cyclic Secondary Azides, Using An Enantioselective Copper-Catalyzed Azide-Alkyne Cycloaddition, Juliana R. Alexander, Amy A. Ott, En Chih Liu, Joseph J. Topczewski

Chemistry Faculty Research & Creative Works

An enantioselective copper-catalyzed azide-alkyne cycloaddition (E-CuAAC) is reported by kinetic resolution. Chiral triazoles were isolated in high yield with limiting alkyne (up to 97:3 enantiomeric ratio (er)). A range of substrates were tolerated (>30 examples), and the reaction was scaled to >1 g. The er of a triazole product could be enhanced by recrystallization and the recovered scalemic azide could be racemized and recycled. Recycling the azide allows efficient use of the undesired azide enantiomer.

Enantioselective Copper Catalyzed Alkyne-Azide Cycloaddition By Dynamic Kinetic Resolution, En Chih Liu, Joseph J. Topczewski

Chemistry Faculty Research & Creative Works

The copper(I) catalyzed alkyne-azide cycloaddition (CuAAC), a click reaction, is one of the most powerful catalytic reactions developed during the last two decades. Conducting CuAAC enantioselectively would add a third dimension to this reaction and would enable the direct synthesis of α-chiral triazoles. Doing so is demanding because the two precursors have linear geometries, and the triazole product is a flat heterocycle. Designing a chiral catalyst is further complicated by the complex mechanism of CuAAC. We report an enantioselective CuAAC (E-CuAAC), enabled by dynamic kinetic resolution (DKR). The E-CuAAC is high yielding and affords up to 99:1 er. The E-CuAAC …

The Benefit Of Precise Chemical Shift And Concentration Referencing In Nmr Applications, Ming Huang

Doctoral Dissertations

“In Nuclear Magnetic Resonance (NMR) spectroscopy, the chemical shift and intensity of NMR signals provide critical information about a sample's molecular structure, reaction conditions, and material properties. For the precise determination of structures and properties, it is critical to know sample or reaction conditions such as temperature, pH, concentration, or absolute amount of material. Chemical-shift and signal-intensity calibrations play a key role for extracting the maximum amount of information from NMR experiments. In this dissertation, internal and external reference standards are used to calibrate NMR spectra with respect to chemical shift and signal intensity. Sealed capillary tubes filled with specific …

Part I: Design, Synthesis, And Studies Of Novel Age-Inhibitors And Age-Breakers; Part Ii: Novel Synthetic Methods For Organofluorine Compound, Jatin Mehta

Doctoral Dissertations

"Novel small molecule inhibitors and breakers of advanced glycation end-products (AGEs) have been synthesized and their in vitro inhibitory activities have been studied by ¹³C NMR, fluorescence, and UV-visible spectroscopy. We have demonstrated that these AGE-inhibitors and AGE-breakers were found to be more effective in their sequestration of AGE intermediates, such as dehydroascorbate (DHA) than the state-of-the art phenacylthiazolium bromide (PTB)-based AGE-inhibitors and AGE-breakers. Citric acid and other polyphenolic antioxidants have substantial AGE inhibitory effects in the D-glucose/leucine or benzylamine Maillard reaction model systems, and thus they are suitable as dietary additives for ameliorating AGE-induced complications.

Organofluorine compounds have …

Metabolic Disorders, Drug Development, Drug Design And Biomarkers, Gjumrakch Aliev, Ramon Cacabelos, V. Prakash Reddy

Chemistry Faculty Research & Creative Works

No abstract provided.

Palladium-Catalyzed Annulation Of 9-Halophenanthrenes With Alkynes: Synthesis, Structural Analysis, And Properties Of Acephenanthrylene-Based Derivatives, En Chih Liu, Min-Kuan Chen, Jen-Yi Li, Yao-Ting Wu

Chemistry Faculty Research & Creative Works

The palladium-catalyzed annulation of 9-bromoand 9-chlorophenanthrenes with alkynes gave 4,5-disubstituted acephenanthrylenes in yields of 58–95% (9 examples). Asymmetric alkynes, such as 1-phenyl-1-propyne, 1-phenyl- 1-hexyne, and 1-cyclopropyl-2-phenylethyne, regioselectively form (cyclo)alkyl-substituted products, following the regular rule that governs the carbopalladation of alkynes. This synthetic protocol can also be utilized in annulations with several p-extended bromoarenes, such as 7-5] helicene, 5- 4] helicene, 9-bromoanthracene, 3-bromoperylene, and 3-bromofluoranthene, to give the corresponding annulated products in moderate to good yields (51–86 %; 6 examples). Similarly, bromocorannulene produced highly curved 1,2-disubstituted cyclopentacorannulenes. Reactions of 6,12-dibromochrysene and 4,7-4] helicene with di(4-tolyl) ethyne provided the twofold annulated products …

Palladium-Catalyzed Reaction Of Haloarenes With Diarylethynes: Synthesis, Structural Analysis, And Properties Of Methylene-Bridged Arenes, Che-Wei Lee, En Chih Liu, Yao-Ting Wu

Chemistry Faculty Research & Creative Works

Fluorenes and methylene-bridged polyarenes were easily and efficiently synthesized from haloarenes (or aryl triflates) and diarylethynes by a one-pot, two-step procedure. This protocol involves the palladium-catalyzed cycloisomerization and a subsequent base-mediated retro-aldol condensation. A major advantage is that the starting materials need not have ortho functional groups to complete the annulation. The backbone of the designed products was enlarged using dihaloarenes, highly π-conjugated haloarenes, or diarylalkynes. The mechanism of the formation of benzo[a]fluorene was investigated. The bowl-shaped structure of methylene-bridged indenocorannulene was verified by X-ray crystallography. The photophysical and electrochemical properties of the products thus prepared were investigated.

Mitochondria- Targeted Antioxidant Skq1 Reverses Glaucomatous Lesions In Rabbits, Elena N. Iomdina, Inna P. Khoroshilova-Maslova, Olga V. Robustova, Olga A. Averina, Nadezhda A. Kovaleva, Gjumrakch Aliev, V. Prakash Reddy, Andrey A. Zamyatnin, Maxim V. Skulachev, Ivan I. Senin, Vladimir P. Skulachev

Chemistry Faculty Research & Creative Works

Glaucoma is the main cause of irreversible blindness worldwide. This disease is characterized by apoptosis of retinal ganglion cells (RGC) and visual field loss that seems to be related to elevated intraocular pressure (IOP). Several lines of evidences have implicated the crucial role of mitochondrial dysfunction in the pathogenesis of glaucoma. Increased mitochondrial oxidative stress in RGC may underlie or contribute to susceptibility of RGC to apoptosis. In our work we (i) designed a rabbit model of chronic, moderately elevated IOP for studying glaucoma and (ii) demonstrated efficacy of mitochondria- Targeted antioxidant SkQ1 as a tool to reverse several traits …

Ru/C: A Simple Heterogeneous Catalyst For The Amination Of Azoles Under Ligand Free Conditions, K. Harsha Vardhan Reddy, B. S.P. Anil Kumar, V. Prakash Reddy, R. Uday Kumar, Y. V.D. Nageswar

Chemistry Faculty Research & Creative Works

A ligand free Ru/C-catalyzed amination of 2-halo azoles with a broad scope of aminating reagents has been developed. A variety of 2-aminoazole derivatives were synthesized in moderate to good yields by utilizing this protocol. The methodology is operationally simple and not sensitive to air and moisture. It provides potentially useful products by using an inexpensive and recyclable catalytic system under ligand free conditions without significant loss of its catalytic activity up to four cycles. This journal is

1-Ferrocenyl-1-Cyclopropyl Cation: The First Long-Lived Cyclopropyl Cation, G. K.Surya Prakash, Herwig Buchholz, V. Prakash Reddy, Armin De Meijere, George A. Olah

Chemistry Faculty Research & Creative Works

No abstract provided.