A new mechanistic insight on β-lactam systems formation from 5-nitroisoxazolidines

RSC Advances ◽  
2015 ◽  
Vol 5 (62) ◽  
pp. 50070-50072 ◽  
Author(s):  
Radomir Jasiński
Keyword(s):  
Dft Calculations ◽  
Ring Opening ◽  
Type Reaction ◽  
Mechanistic Insight

DFT calculations at various theory levels unequivocally show that conversion of 5-nitroisoxazolidines into β-lactams does not take place via a ring opening step (as hitherto suggested), but takes place according to a three-step, domino-type reaction.

scholarly journals Synergistic catalysis: enantioselective cyclopropanation of alkylidene benzoxazoles by Pd(ii) and secondary amine catalysis. Scope, limitations and mechanistic insight

2018 ◽  
Vol 5 (5) ◽  
pp. 806-812 ◽  
Author(s):  
Marta Meazza ◽  
Victor Polo ◽  
Pedro Merino ◽  
Ramon Rios
Keyword(s):  
Dft Calculations ◽  
Secondary Amine ◽  
Ring Opening ◽  
Synergistic Catalysis ◽  
Mechanistic Insight ◽  
Amine Catalysis

An enantioselective synergistic cascade cyclopropanation/NHC catalyzed ring opening has been reported. DFT calculations have been performed to confirm the mechanism.

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>

scholarly journals Fates of imine intermediates in radical cyclizations of N-sulfonylindoles and ene-sulfonamides

2015 ◽  
Vol 11 ◽  
pp. 1649-1655 ◽  
Author(s):  
Hanmo Zhang ◽  
E Ben Hay ◽  
Stephen J Geib ◽  
Dennis P Curran
Keyword(s):  
Carbonyl Group ◽  
Ring Opening ◽  
Radical Cyclizations ◽  
Type Reaction ◽  
Primary Products ◽  
Lactam Carbonyl Group ◽  
Lactam Carbonyl ◽  
Imine Reduction ◽  
Derivatives Of

Two new fates of imine intermediates formed on radical cyclizations of ene-sulfonamides have been identified, reduction and hydration/fragmentation. Tin hydride-mediated cyclizations of 2-halo-N-(3-methyl-N-sulfonylindole)anilines provide spiro[indoline-3,3'-indolones] or spiro-3,3'-biindolines (derived from imine reduction), depending on the indole C2 substituent. Cyclizations of 2-haloanilide derivatives of 3-carboxy-N-sulfonyl-2,3-dihydropyrroles also presumably form spiro-imines as primary products. However, the lactam carbonyl group facilitates the ring-opening of these cyclic imines by a new pathway of hydration and retro-Claisen-type reaction, providing rearranged 2-(2'-formamidoethyl)oxindoles.

Mechanistic insight into initiation and regioselectivity in the copolymerization of epoxides and anhydrides by Al complexes

2020 ◽  
Vol 56 (90) ◽  
pp. 14027-14030
Author(s):  
Yanay Popowski ◽  
Juan J. Moreno ◽  
Asa W. Nichols ◽  
Shelby L. Hooe ◽  
Caitlin J. Bouchey ◽  
...  
Keyword(s):  
Ring Opening ◽  
Mechanistic Insight ◽  
Insight Into

Pentacoordinate Al catalysts comprising bipyridine (bpy) and phenanthroline (phen) backbones were synthesized, their activity in epoxide/anhydride copolymerization studied, and the products of stoichiometric ring-opening of anhydrides characterized.

scholarly journals An Efficient and Mild Method for the Synthesis and Hydrazinolysis ofN-Glyoxylamino Acid Esters

2013 ◽  
Vol 2013 ◽  
pp. 1-6 ◽  
Author(s):  
Ayman El-Faham ◽  
Zainab Al Marhoon ◽  
Ahmed Abdel-Megeed ◽  
Mohamed Siddiqui
Keyword(s):  
Hydrazine Hydrate ◽  
Good Yield ◽  
Acid Ester ◽  
Ring Opening ◽  
Acid Hydrazide ◽  
Type Reaction ◽  
H Nmr ◽  
Elemental Microanalysis ◽  
Acid Esters ◽  
C Nmr

N-Glyoxylamino acid ester derivatives were synthesized via the ring opening ofN-acetylisatin using moderate conditions. During the hydrazinolysis ofN-glyoxylamino acid ester derivatives with hydrazine hydrate (80%) in methanol, unexpected reduction of theα-keto group occurred to affordN-acylamino acid hydrazide derivatives in good yield (80–90%) (Wolff-Kishner type reaction). All the synthesized compounds were characterized by1H NMR,13C NMR, and elemental microanalysis.

scholarly journals Alumination of Aryl Methyl Ethers: Switching Between Sp2 and Sp3 C–O Bond Functionalisation with Pd-Catalysis

2021 ◽  
Author(s):  
Ryan Brown ◽  
Thomas N hooper ◽  
Feriel Rekroukh ◽  
Andrew J. P. White ◽  
Paulo J. Costa ◽  
...  
Keyword(s):  
Dft Calculations ◽  
Oxidative Addition ◽  
Starting Material ◽  
Aromatic Molecules ◽  
Kinetic Isotope ◽  
Mechanistic Insight ◽  
Sn2 Pathway ◽  
Aryl Methyl

The reaction of [{(ArNCMe)2CH}Al] (Ar = 2,6-di-iso-propylphenyl, 1) with aryl methyl ethers proceeded with alumination of the sp3 C–O bond by a presumed SN2 pathway. The selectivity of this reaction could be switched by inclusion of a catalyst. In the presence of [Pd(PCy3)2], chemoselective sp2 C–O bond functionalisation was observed. Kinetic isotope experiments and DFT calculations support a catalytic pathway involving the ligand-assisted oxidative addition of the sp2 C–O bond to a Pd---Al intermetallic complex. The net result of both non-catalysed and catalytic pathways is the generation of polar organoaluminium complexes from aryl methyl ethers with complete atom-efficiency. Switches in selectivity yield isomeric products from a single starting material. The methodology (and mechanistic insight) holds promise as a means to functionalise aromatic molecules derived from lignin depolymerisation and we demonstrate an application to a derivative of vanillin.

Why electrostatically enhanced thiourea is better than Schreiner's thiourea in both catalytic activity and regioselectivity?

2019 ◽  
Vol 6 (11) ◽  
pp. 1821-1831 ◽  
Author(s):  
Chao-Xian Yan ◽  
Rui-Zhi Wu ◽  
Ka Lu ◽  
Fang-Ling Yang ◽  
Xiao-Shan Yang ◽  
...  
Keyword(s):  
Catalytic Activity ◽  
Dft Calculations ◽  
Ring Opening ◽  
Styrene Oxide ◽  
Better Than

Electrostatically enhanced thiourea is more active and efficient than Schreiner's thiourea in the ring-opening aminolysis of styrene oxide with aniline, and the underlying reasons were explored by DFT calculations.

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