scholarly journals The Lord of the Chemical Rings: Catalytic Synthesis of Important Industrial Epoxide Compounds

Catalysts ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 765
Author(s):  
Yudong Meng ◽  
Francesco Taddeo ◽  
Adriana Freites Aguilera ◽  
Xiaoshuang Cai ◽  
Vincenzo Russo ◽  
...  
Keyword(s):  
Vegetable Oil ◽  
Functional Group ◽  
Enzymatic Catalysis ◽  
Catalytic Synthesis ◽  
Membered Ring ◽  
Catalytic Systems ◽  
Ring Strain ◽  
Oxirane Group ◽  
Review Articles ◽  
Fine Chemistry

The epoxidized group, also known as the oxirane group, can be considered as one of the most crucial rings in chemistry. Due to the high ring strain and the polarization of the C–O bond in this three-membered ring, several reactions can be carried out. One can see such a functional group as a crucial intermediate in fuels, polymers, materials, fine chemistry, etc. Literature covering the topic of epoxidation, including the catalytic aspect, is vast. No review articles have been written on the catalytic synthesis of short size, intermediate and macro-molecules to the best of our knowledge. To fill this gap, this manuscript reviews the main catalytic findings for the production of ethylene and propylene oxides, epichlorohydrin and epoxidized vegetable oil. We have selected these three epoxidized molecules because they are the most studied and produced. The following catalytic systems will be considered: homogeneous, heterogeneous and enzymatic catalysis.

Catalytic Synthesis of Cyclic Guanidines via Hydrogen Atom Transfer and Radical-Polar Crossover

2020 ◽  
Author(s):  
Shunya Ohuchi ◽  
Hiroki Koyama ◽  
Hiroki Shigehisa
Keyword(s):  
Hydrogen Atom ◽  
Functional Group ◽  
Hydrogen Atom Transfer ◽  
Catalytic Synthesis ◽  
Membered Ring ◽  
Biologically Active ◽  
Atom Transfer ◽  
Powerful Method ◽  
Protective Groups ◽  
The Common

A catalytic synthesis of cyclic guanidines, which are found in many biologically active compounds and natu-ral products, was developed, wherein transition-metal hydrogen atom transfer and radical-polar crossover were employed. This mild and functional-group tolerant process enabled the cyclization of alkenyl guanidines bearing common protective groups, such as Cbz and Boc. This powerful method not only provided the common 5- and 6-membered rings but also an unusual 7-membered ring. The derivatization of the products afforded various heterocycles. We also investigated the se-lective cyclization of mono-protected or hetero-protected (TFA and Boc) alkenyl guanidines and their further derivatiza-tions.

scholarly journals Catalytic Synthesis of Cyclic Guanidines via Hydrogen Atom Transfer and Radical-Polar Crossover

2020 ◽  
Author(s):  
Shunya Ohuchi ◽  
Hiroki Koyama ◽  
Hiroki Shigehisa
Keyword(s):  
Hydrogen Atom ◽  
Functional Group ◽  
Hydrogen Atom Transfer ◽  
Catalytic Synthesis ◽  
Membered Ring ◽  
Biologically Active ◽  
Synthetic Method ◽  
Atom Transfer ◽  
Powerful Method ◽  
Protective Groups

Cyclic guanidines are found in many biologically active compounds and natural products. Further, the for-mation of the atypical 7-membered ring of cyclic guanidine remains challenging due to a lack of efficient preparation strategies and low yield. Herein, a catalytic synthetic method for cyclic guanidines was developed via transition-metal hydrogen atom transfer and radical-polar crossover. This mild and functional-group tolerant process enabled the cycliza-tion of an alkenyl guanidines bearing common protective groups, such as Cbz and Boc groups. This powerful method not only provided typical 5- and 6-membered rings but also the atypical 7-membered ring. The derivatization of the products afforded various heterocycles. We also investigated the selective cyclization of mono-protected or hetero-protected (TFA and Boc) alkenyl guanidines and their further derivatizations.

scholarly journals Catalytic Synthesis of Cyclic Guanidines via Hydrogen Atom Transfer and Radical-Polar Crossover

2020 ◽  
Author(s):  
Shunya Ohuchi ◽  
Hiroki Koyama ◽  
Hiroki Shigehisa
Keyword(s):  
Hydrogen Atom ◽  
Functional Group ◽  
Hydrogen Atom Transfer ◽  
Catalytic Synthesis ◽  
Membered Ring ◽  
Biologically Active ◽  
Synthetic Method ◽  
Atom Transfer ◽  
Powerful Method ◽  
Protective Groups

Cyclic guanidines are found in many biologically active compounds and natural products. Further, the for-mation of the atypical 7-membered ring of cyclic guanidine remains challenging due to a lack of efficient preparation strategies and low yield. Herein, a catalytic synthetic method for cyclic guanidines was developed via transition-metal hydrogen atom transfer and radical-polar crossover. This mild and functional-group tolerant process enabled the cycliza-tion of an alkenyl guanidines bearing common protective groups, such as Cbz and Boc groups. This powerful method not only provided typical 5- and 6-membered rings but also the atypical 7-membered ring. The derivatization of the products afforded various heterocycles. We also investigated the selective cyclization of mono-protected or hetero-protected (TFA and Boc) alkenyl guanidines and their further derivatizations.

Nickel-Catalyzed Inter- and Intramolecular Carbon-Sulfur Bond Metathesis by Reversible Arylation

2019 ◽  
Author(s):  
Tristan Delcaillau ◽  
Alessandro Bismuto ◽  
Zhong Lian ◽  
Bill Morandi
Keyword(s):  
Good Yield ◽  
Functional Group ◽  
Product Formation ◽  
Single Bond ◽  
Ring Closing Metathesis ◽  
Catalytic Systems ◽  
Metathesis Reactions ◽  
New Applications ◽  
Further Development ◽  
Sulfur Bond

A nickel-catalyzed carbon-sulfur bond metathesis has been developed to access high-value thioethers. 1,2-bis(dicyclohexylphosphino)ethane (dcype) is essential to promote this highly functional group tolerant reaction. Further, synthetically challenging macrocycles could be obtained in good yield in an unusual example of ring-closing metathesis which does not involve alkene bonds. In-depth organometallic studies support a reversible Ni(0)-Ni(II) pathway to product formation. Overall, this work does not only disclose a more sustainable and more functional group tolerant alternative to previous catalytic systems based on Pd, but also presents new applications and mechanistic information which are highly relevant to the further development and application of unusual single bond metathesis reactions.

Chiral imidazolidinones: A class of priviliged organocatalysts in stereoselective organic synthesis

2020 ◽  
Vol 5 (5) ◽  
Author(s):  
Laura Raimondi ◽  
Chiara Faverio ◽  
Monica Fiorenza Boselli
Keyword(s):  
Pharmaceutical Industry ◽  
Green Chemistry ◽  
Organic Synthesis ◽  
Catalytic Synthesis ◽  
Biological Chemistry ◽  
Chiral Molecules ◽  
Catalytic Systems ◽  
Drug Synthesis ◽  
Industry Needs

AbstractChiral molecules hold a mail position in Organic and Biological Chemistry, so pharmaceutical industry needs suitable strategies for drug synthesis. Moreover, Green Chemistry procedures are increasingly required in order to avoid environment deterioration. Catalytic synthesis, in particular organocatalysis, in thus a continuously expanding field. A survey of more recent researches involving chiral imidazolidinones is here presented, with a particular focus on immobilized catalytic systems.

Delineating the possibilities for intramolecular interception of the squarate ester cascade through the use of metalated enecarbamates

2000 ◽  
Vol 78 (6) ◽  
pp. 689-696 ◽  
Author(s):  
Jinsung Tae ◽  
Leo A Paquette
Keyword(s):  
Ring Opening ◽  
Membered Ring ◽  
Sequential Treatment ◽  
Nucleophilic Attack ◽  
Ring Strain ◽  
Multistep Process

Highly functionalized and annulated 2,4-cyclooctadienones are formed in a stereoselective manner by sequential treatment of squarate esters with a lithiated enecarbamate (six-membered ring or larger) and a cycloalkenyl- or 1-alkenyllithium reagent. The mechanistic details of this multistep process are presented. Particular attention is drawn to the step that involves intramolecular nucleophilic attack by a proximal oxido anion at the carbamate carbonyl and results in redirection of the cascade. This step is thwarted when five-membered cyclic enecarbamates are employed because of the excessive buildup of ring strain in the associated transition state.Key words: squarate esters, enecarbamates, conrotatory ring opening, intramolecular acylation, alkenyllithium reagents.

scholarly journals Addition of lithiated enol ethers to nitrones and subsequent Lewis acid induced cyclizations to enantiopure 3,6-dihydro-2H-pyrans – an approach to carbohydrate mimetics

2010 ◽  
Vol 6 ◽  
Author(s):  
Fabian Pfrengle ◽  
Hans-Ulrich Reissig
Keyword(s):  
Lewis Acid ◽  
Functional Group ◽  
Tricarboxylic Acid ◽  
Membered Ring ◽  
Enol Ether ◽  
Enol Ethers ◽  
Acidic Conditions ◽  
Hydroxylamine Derivatives

A stereodivergent synthesis of enantiopure 3,6-dihydro-2H-pyrans is presented. The addition of lithiated enol ethers to carbohydrate-derived nitrones afforded syn- or anti-configured hydroxylamine derivatives 4a–d that were cyclized under Lewis acidic conditions to yield functionalized dihydropyrans cis- or trans-5a–d containing an enol ether moiety. This functional group was employed for a variety of subsequent reactions such as dihydroxylation or bromination. Bicyclic enol ether 19 was oxidatively cleaved to provide the highly functionalized ten-membered ring lactone 20. The synthesized enantiopure aminopyrans 24, 26, 28 and 30 can be regarded as carbohydrate mimetics. Trimeric versions of 24 and 28 were constructed via their attachment to a tricarboxylic acid core.

scholarly journals Olefin metathesis in air

2015 ◽  
Vol 11 ◽  
pp. 2038-2056 ◽  
Author(s):  
Lorenzo Piola ◽  
Fady Nahra ◽  
Steven P Nolan
Keyword(s):  
Transition Metal ◽  
Olefin Metathesis ◽  
Functional Group ◽  
High Oxidation State ◽  
Catalytic Systems ◽  
Metal Centers ◽  
Early Transition Metal ◽  
Significant Interest ◽  
High Oxidation ◽  
Metathesis Catalysts

Since the discovery and now widespread use of olefin metathesis, the evolution of metathesis catalysts towards air stability has become an area of significant interest. In this fascinating area of study, beginning with early systems making use of high oxidation state early transition metal centers that required strict exclusion of water and air, advances have been made to render catalysts more stable and yet more functional group tolerant. This review summarizes the major developments concerning catalytic systems directed towards water and air tolerance.

Palladium-catalyzed [4 + 3] dearomatizing cycloaddition reaction of N-iminoquinolinium ylides

2020 ◽  
Vol 7 (18) ◽  
pp. 2612-2617
Author(s):  
Wenhao Dai ◽  
Chunpu Li ◽  
Yichu Liu ◽  
Xu Han ◽  
Xingjun Li ◽  
...  
Keyword(s):  
Functional Group ◽  
Cycloaddition Reaction ◽  
Membered Ring ◽  
Efficient Approach ◽  
Mild Conditions ◽  
Palladium Catalyzed

An efficient approach to obtain saturated seven-membered ring containing three heteroatoms has been developed by using a palladium-catalyzed [4 + 3] dearomatizing cycloaddition. This approach features mild conditions and good functional group tolerance.

Couplings into Methylene Groups: a New Nuclear Magnetic Resonance Approach to Stereochemistry

1971 ◽  
Vol 49 (17) ◽  
pp. 2874-2884 ◽  
Author(s):  
K. N. Slessor ◽  
A. S. Tracey
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Membered Ring ◽  
Coupling Constants ◽  
Ratio Method ◽  
Dihedral Angles ◽  
Ring Strain ◽  
Molecular Features ◽  
Conformational Preferences ◽  
Methylene Groups ◽  
Ring Puckering

A method of assigning dihedral angles to hydrogens adjacent to a methylene function by using computer analyzed n.m.r. coupling constants in a modified Karplus equation is presented. The "Dihedral Angle Estimation by the Ratio Method" (DAERM) is based on the assumption that, although the magnitudes of the Karplus constants, k1 and k2, vary, the ratio of k1 to k2 is a constant. Dihedral angles computed in this way seem not to be influenced by the effects of ring strain and substituent electronegativity. The conformational preferences of several four- to six-membered ring Systems, some containing oxygen and sulfur atoms, have been investigated by this method. Molecular features such as ring puckering and flattening are indicated by DAERM as are some subtle electrostatic influences.

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