Mechanistic understanding of [Rh(NHC)]-catalyzed intramolecular [5 + 2] cycloadditions of vinyloxiranes and vinylcyclopropanes with alkynes

2018 ◽  
Vol 16 (23) ◽  
pp. 4295-4303 ◽  
Author(s):  
Huan Zhou ◽  
Botao Wu ◽  
Jun-An Ma ◽  
Yanfeng Dang
Keyword(s):  
Reductive Elimination ◽  
Mechanistic Understanding ◽  
Oxirane Cleavage

Rh-catalyzed hetero-[5 + 2] cycloaddition of vinyloxirane with alkyne occurs via oxidative alkyne–alkene cyclization, oxirane cleavage and reductive elimination, the first example where oxidative alkyne–alkene cyclization mechanism is preferred within Rh-catalyzed [5 + 2] cycloadditions.

Reversible Oxidative-Addition and Reductive-Elimination of Thiophene from a Titanium Complex and Its Thermally-Induced Hydrodesulfurization Chemistry

2019 ◽  
Author(s):  
Alejandra Gomez-Torres ◽  
J. Rolando Aguilar-Calderón ◽  
Carlos Saucedo ◽  
Aldo Jordan ◽  
Alejandro J. Metta-Magaña ◽  
...  
Keyword(s):  
Dft Calculations ◽  
Ring Opening ◽  
Thiophene Ring ◽  
Oxidative Addition ◽  
Reductive Elimination ◽  
Thermally Induced ◽  
Titanium Complex

<p>The masked Ti(II) synthon (<sup>Ket</sup>guan)(<i>η</i><sup>6</sup>-Im<sup>Dipp</sup>N)Ti (<b>1</b>) oxidatively adds across thiophene to give ring-opened (<sup>Ket</sup>guan)(Im<sup>Dipp</sup>N)Ti[<i>κ</i><sup>2</sup>-<i>S</i>(CH)<sub>3</sub><i>C</i>H] (<b>2</b>). Complex <b>2</b> is photosensitive, and upon exposure to light, reductively eliminates thiophene to regenerate <b>1</b> – a rare example of early-metal mediated oxidative-addition/reductive-elimination chemistry. DFT calculations indicate strong titanium π-backdonation to the thiophene π*-orbitals leads to the observed thiophene ring opening across titanium, while a proposed photoinduced LMCT promotes the reverse thiophene elimination from <b>2</b>. Finally, pressurizing solutions of <b>2 </b>with H<sub>2</sub> (150 psi) at 80 °C leads to the hydrodesulfurization of thiophene to give the Ti(IV) sulfide (<sup>Ket</sup>guan)(Im<sup>Dipp</sup>N)Ti(S) (<b>3</b>) and butane. </p>

S(IV)–Mediated Unsymmetrical Heterocycle Cross-Couplings

2019 ◽  
Author(s):  
Min Zhou ◽  
Jet Tsien ◽  
Tian Qin
Keyword(s):  
Cross Coupling ◽  
Reductive Elimination ◽  
Facile Synthesis ◽  
Trigonal Bipyramidal

<p>Herein we report a sulfur (IV) mediated cross-coupling for facile synthesis of heteroaromatic substrates. Addition of heteroaryl nucleophiles onto a simple, readily-accessible alkyl sulfinyl (IV) chloride allows formation of a trigonal bipyramidal sulfurane intermediate. Reductive elimination therefrom provides bis-heteroaryl products in a practical and efficient fashion. <br></p>

Carbon-Heteroatom Cross-Coupling via an Electronically Excited Nickel (II) Complex

2019 ◽  
Author(s):  
Randolph Escobar ◽  
Jeffrey Johannes
Keyword(s):  
Energy Transfer ◽  
Functional Groups ◽  
Cross Coupling ◽  
Reductive Elimination ◽  
Aryl Halides ◽  
Coupling Reactions ◽  
General Methodology ◽  
Cross Coupling Reactions ◽  
Electronically Excited ◽  
Energy Transfer Pathway

<div>While carbon-heteroatom cross coupling reactions have been extensively studied, many methods are specific and</div><div>limited to a set of substrates or functional groups. Reported here is a method that allows for C-O, C-N and C-S cross coupling reactions under one general methodology. We propose that an energy transfer pathway, in which an iridium photosensitizer produces an excited nickel (II) complex, is responsible for the key reductive elimination step that couples aryl halides to 1° and 2° alcohols, anilines, thiophenols, carbamates and sulfonamides.</div>

From Ocean to Bedside: the Therapeutic Potential of Molluscan Hemocyanins

2018 ◽  
Vol 25 (20) ◽  
pp. 2292-2303 ◽  
Author(s):  
Negar Talaei Zanjani ◽  
Monica Miranda Saksena ◽  
Fariba Dehghani ◽  
Anthony L. Cunningham
Keyword(s):  
Antiviral Activity ◽  
Clinical Efficacy ◽  
Mechanism Of Action ◽  
Therapeutic Agent ◽  
Marine Invertebrates ◽  
Therapeutic Potential ◽  
Biological Functions ◽  
Anticancer Properties ◽  
Mechanistic Understanding

Hemocyanins are large and versatile glycoproteins performing various immunological and biological functions in many marine invertebrates including arthropods and molluscs. This review discusses the various pharmacological applications of mollusc hemocyanin such as antiviral activity, immunostimulatory and anticancer properties that have been reported in the literature between the years 2000 and 2016. Emphasis is placed on a better mechanistic understanding of hemocyanin as a therapeutic agent. Elucidation of the mechanism of action is essential to improve the clinical efficacy and for a better understanding of some endogenous immunological functions of this complex glycoprotein.

Kinetics Studies of Epoxidation and Oxirane Cleavage-Epoxidized Palm Kernel Oil

2020 ◽  
Vol 13 (3) ◽  
pp. 232-240
Author(s):  
Mohd Jumain Jalil ◽  
Aliff Farhan Mohd Yamin ◽  
Mohd Saufi Md Zaini ◽  
Veronique Gloria V. Siduru ◽  
Norhashimah Morad ◽  
...  
Keyword(s):  
Fatty Acids ◽  
Reference Material ◽  
Palm Kernel ◽  
High Yield ◽  
Simulation Data ◽  
Kinetic Rate ◽  
Palm Kernel Oil ◽  
Kinetics Studies ◽  
Kernel Oil ◽  
Oxirane Cleavage

Background: Studies pertaining to the epoxidation of fatty acids, garnered much interest in recent years due to the rising demand of eco-friendly epoxides derived from vegetable oils. Methods: Epoxide is an important chemical precursor for the production of alcohols, glycols and polymers, like polyesters and epoxy resin. Epoxidation is the name given to the reaction when the double bonds are converted into epoxide. Results: Temperature at 55oC was used as a reference material in the epoxide process, as it produces a high yield epoxide being 88%. The kinetic rate of epoxidized palm kernel oil, k was obtained to be k11= 0.5125, k12= 0.05045, k21= 0.03185, k41= 0.01 and k51= 0.01243. Conclusion: Hence, by fitting the result with the experimental work and simulation, the summation of error being stimulated by I-sight simulation was 0.731116428 and the correlation between the experimental and simulation data was 0.925544.

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