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.

scholarly journals Synergistic formal ring contraction for the enantioselective synthesis of spiropyrazolones

2018 ◽  
Vol 9 (30) ◽  
pp. 6368-6373 ◽  
Author(s):  
Marta Meazza ◽  
Martin Kamlar ◽  
Lucie Jašíková ◽  
Bedřich Formánek ◽  
Andrea Mazzanti ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Infrared Spectroscopy ◽  
Dft Calculations ◽  
Secondary Amine ◽  
Protonated Form ◽  
Enantioselective Synthesis ◽  
Ring Contraction ◽  
Mechanistic Pathway ◽  
Amine Catalysis

We report the first ring contraction/formal [6 + 2] cycloaddition using synergistic Pd(0)/secondary amine catalysis, obtaining [5,5]-spiropyrazolone derivatives in excellent yields and stereoselectivities. We detected the key palladium activated intermediate in its protonated form by mass spectrometry and characterized its structure by infrared spectroscopy and DFT calculations, allowing us to propose a conceivable mechanistic pathway for this reaction.

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.

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>

Regio-, Stereo- and Enantioselective α-Addition of Carbonyl Nucleo-philes to Allenamides Catalyzed by a Synergistic Copper/Enamine System

2020 ◽  
Author(s):  
Rémi Blieck ◽  
Sebastien Lemouzy ◽  
Marc Taillefer ◽  
Florian Monnier
Keyword(s):  
Catalytic System ◽  
Secondary Amine ◽  
Primary Amine ◽  
Synergistic Catalysis ◽  
Enantioselective Addition ◽  
Amine Catalysts

A dual copper/enamine catalytic system is found to enable an intermolecular enantioselective α-addition of various carbonyl nucleophiles to allenamides. Secondary amine catalysts allowed the highly enantioselective addition of aldehydes, while using primary amine catalysts led to the enantioselective addition of ketoester nucleophiles. The process was found to be highly regio-, stereo- and enantio-selective and represented the first allene hydrofunctionalization using an synergistic catalysis involving copper

Break the template boundary: Test of different protein scaffolds by genetic code expansion resulted in NADPH-dependent secondary amine catalysis

2021 ◽  
Author(s):  
Thomas Williams ◽  
Yu-Hsuan Tsai ◽  
Louis Luk
Keyword(s):  
Genetic Code ◽  
Secondary Amine ◽  
Transfer Hydrogenation ◽  
Protein Scaffolds ◽  
Artificial Enzyme ◽  
Enzyme Design ◽  
Catalytically Active ◽  
Amine Catalysis ◽  
Genetic Code Expansion ◽  
Distinctive Role

Abstract Here, incorporation of secondary amine by genetic code expansion was used to expand the potential protein templates for artificial enzyme design. Pyrrolysine analogue containing a D-proline could be stably incorporated into proteins, including the multidrug-binding LmrR and nucleotide-binding dihydrofolate reductase (DHFR). Both modified scaffolds were catalytically active, mediating transfer hydrogenation with a relaxed substrate scope. The protein templates played a distinctive role in that, while the LmrR variants were confined to the biomimetic BNAH as the hydride source, the optimal DHFR variant favorably used the pro-R hydride from NADPH for reactions. Due to the cofactor compatibility, the DHFR secondary amine catalysis could also be coupled to an enzymatic recycling scheme. This work has illustrated the unique advantages of using proteins as hosts, and thus the presented concept is expected to find uses in enabling tailored secondary amine catalysis.

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 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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