Advancing macromolecular hoop construction: recent developments in synthetic cyclic polymer chemistry

2021 ◽  
Vol 12 (7) ◽  
pp. 958-969
Author(s):  
Teng-Wei Wang ◽  
Matthew R. Golder
Keyword(s):  
Ring Expansion ◽  
Ring Closure ◽  
Polymer Chemistry ◽  
Linear Polymers ◽  
Synthetic Methodology ◽  
Cyclic Polymer ◽  
Recent Developments

Synthetic methodology to access cyclic macromolecules continues to develop via two distinct mechanistic classes: ring-expansion of macrocyclic initiators and ring-closure of functionalized linear polymers.

Recent Developments in the Asymmetric Detrifluoroacetylative Reactions of in situ Generated Mono-Fluorinated Enolates

2020 ◽  
Vol 24 (18) ◽  
pp. 2181-2191
Author(s):  
Li Wang ◽  
Ziyi Li ◽  
Jiang Liu ◽  
Jianlin Han ◽  
Hiroki Moriwaki ◽  
...  
Keyword(s):  
Organic Chemistry ◽  
Bond Cleavage ◽  
Synthetic Methodology ◽  
Research Topics ◽  
Synthetic Organic Chemistry ◽  
Nucleophilic Reactions ◽  
F Center ◽  
Recent Developments

The development of an efficient and mild synthetic methodology for the construction of bioactive fluorine-containing molecules represents one of the hot research topics in general synthetic organic chemistry. In this review, some recent progresses achieved in the development of detrifluoroacetylatively generated mono-fluorinated enolates via CC bond cleavage and their asymmetric nucleophilic reactions for assembly of chiral quaternary C-F center containing compounds.

scholarly journals Nitrile Synthesis with Aldoxime Dehydratases: A Biocatalytic Platform with Applications in Asymmetric Synthesis, Bulk Chemicals, and Biorefineries

Molecules ◽  
2021 ◽  
Vol 26 (15) ◽  
pp. 4466
Author(s):  
Pablo Domínguez de María
Keyword(s):  
Asymmetric Synthesis ◽  
Organic Solvents ◽  
Raw Materials ◽  
Aqueous Media ◽  
Industrial Processes ◽  
Polymer Chemistry ◽  
Fine Chemicals ◽  
Mild Conditions ◽  
Bulk Chemicals ◽  
Recent Developments

Nitriles comprise a broad group of chemicals that are currently being industrially produced and used in fine chemicals and pharmaceuticals, as well as in bulk applications, polymer chemistry, solvents, etc. Aldoxime dehydratases catalyze the cyanide-free synthesis of nitriles starting from aldoximes under mild conditions, holding potential to become sustainable alternatives for industrial processes. Different aldoxime dehydratases accept a broad range of aldoximes with impressive high substrate loadings of up to >1 Kg L−1 and can efficiently catalyze the reaction in aqueous media as well as in non-aqueous systems, such as organic solvents and solvent-free (neat substrates). This paper provides an overview of the recent developments in this field with emphasis on strategies that may be of relevance for industry and sustainability. When possible, potential links to biorefineries and to the use of biogenic raw materials are discussed.

Synthesis of 5-Aryl- 1,4-benzoxazepine and 6-phenyl-2H-1,5-benzoxazocine derivatives

1984 ◽  
Vol 37 (1) ◽  
pp. 129 ◽  
Author(s):  
JB Bremner ◽  
EJ Browne ◽  
IWK Gunawardana
Keyword(s):  
Aromatic Ring ◽  
Sodium Tetrahydroborate ◽  
Phosphorus Oxychloride ◽  
Ring Expansion ◽  
Ring Closure ◽  
Dilute Solution ◽  
Type Reaction ◽  
Chlorine Substituent

Four 5-aryl-2,3-dihydro-1,4-benzoxazepines (5a-d), with electron-releasing substituents, were prepared by a Bischler-Napieralski-type reaction of N-(2-aryloxyethyl)benzamides with phosphorus oxychloride in butanenitrile or ethanenitrile. Analogous 2,3-dihydro-1,4-benzoxazepines (12a, b), with hydrogen only or a chlorine substituent in the fused aromatic ring, were prepared by C-N ring-closure reactions. Cyclization of a dilute solution of N-[3-(3-methoxyphenoxy)propyl]benzamide (21) with phosphorus oxychloride in ethanenitrile gave a 40% yield of 9-methoxy-6-phenyl-3,4-dihydro- 2H-1,5-benzoxazocine (22). The seven- and eight-membered cyclic imines were converted into their methiodide salts (6a-d), (15a,b) and (24). These were reduced with sodium tetrahydroborate to yield the 5-aryl-4-methyl-2,3,4,5-tetrahydro-1,4-benzoxazepines (7a-d) and (l6a,b), and the 9-methoxy- 5-methyl-6-phenyl-3,4,5,6-tetrahydro-2H-1,5-benzoxazocine (25). These products were prepared for use as starting materials in ring-expansion reactions through the Meisenheimer rearrangement.

Interconversion of Nitrenes, Carbenes, and Nitrile Ylides by Ring Expansion, Ring Opening, Ring Contraction, and Ring Closure: 3-Quinolylnitrene, 2-Quinoxalylcarbene, and 3-Quinolylcarbene

2009 ◽  
Vol 62 (3) ◽  
pp. 275 ◽  
Author(s):  
David Kvaskoff ◽  
Ullrich Mitschke ◽  
Chris Addicott ◽  
Justin Finnerty ◽  
Pawel Bednarek ◽  
...  
Keyword(s):  
Ir Spectra ◽  
Ring Opening ◽  
Density Functional ◽  
Diazo Compound ◽  
Density Functional Theory Calculations ◽  
Ring Expansion ◽  
Uv Spectra ◽  
Ring Closure ◽  
High Yield ◽  
Uv And Ir Spectra

Photolysis of 3-azidoquinoline 6 in an Ar matrix generates 3-quinolylnitrene 7, which is characterized by its electron spin resonance (ESR), UV, and IR spectra in Ar matrices. Nitrene 7 undergoes ring opening to a nitrile ylide 19, also characterized by its UV and IR spectra. A subsequent 1,7-hydrogen shift in the ylide 19 affords 3-(2-isocyanophenyl)ketenimine 20. Matrix photolysis of 1,2,3-triazolo[1,5-c]quinoxaline 26 generates 4-diazomethylquinazoline 27, followed by 4-quinazolylcarbene 28, which is characterized by ESR and IR spectroscopy. Further photolysis of carbene 28 slowly generates ketenimine 20, thus suggesting that ylide 19 is formed initially. Flash vacuum thermolysis (FVT) of both 6 and 26 affords 3-cyanoindole 22 in high yield, thereby indicating that carbene 28 and nitrene 7 enter the same energy surface. Matrix photolysis of 3-quinolyldiazomethane 30 generates 3-quinolylcarbene 31, which on photolysis at >500 nm reacts with N2 to regenerate diazo compound 30. Photolysis of 30 in the presence of CO generates a ketene (34). 3-Quinolylcarbene 31 cyclizes on photolysis at >500 nm to 5-aza-2,3-benzobicyclo[4.1.0]hepta-2,4,7-triene 32. Both 31 and 32 are characterized by their IR and UV spectra. FVT of 30 yields a mixture of 2- and 3-cyanoindenes via a carbene–carbene–nitrene rearrangement 31 → 2-quinolylcarbene 39 → 1-naphthylnitrene 43. The reaction mechanisms are supported by density functional theory calculations of the energies and spectra of all relevant ground and transition state structures at the B3LYP/6–31G* level.

Topological Polymer Chemistry Enters Surface Science: Linear versus Cyclic Polymer Brushes

2016 ◽  
Vol 128 (50) ◽  
pp. 15812-15817 ◽  
Author(s):  
Giulia Morgese ◽  
Lucca Trachsel ◽  
Matteo Romio ◽  
Mohammad Divandari ◽  
Shivaprakash N. Ramakrishna ◽  
...  
Keyword(s):  
Surface Science ◽  
Polymer Brushes ◽  
Polymer Chemistry ◽  
Cyclic Polymer

Molecular Theories of Rubberlike Elasticity and Polymer Viscoelasticity

1972 ◽  
Vol 45 (3) ◽  
pp. 638-666 ◽  
Author(s):  
Mitchel Shen ◽  
William F. Hall ◽  
Roger E. Dewames
Keyword(s):  
Physical Properties ◽  
Configurational Entropy ◽  
Polymer Chains ◽  
Elastic Response ◽  
Linear Polymers ◽  
Polymer Molecules ◽  
Recent Developments ◽  
Conformational Statistics ◽  
Polymer Viscoelasticity

Abstract The foundation for nearly all the molecular theories of the physical properties of polymers was laid in 1934 when Guth and Mark and Kuhn first recognized the role of configurational entropy of polymer chains. By virtue of ability of their segments to rotate with respect to each other along the chain backbone, macromolecules are capable of assuming a myriad of conformations. It is this long, flexible chain nature of polymer molecules that provides us a link in interpreting the macroscopic physical properties in terms of microscopic molecular dynamics. In this review we shall demonstrate the utilization of conformational statistics in the formulation of molecular theories for two important aspects of the mechanical properties of polymers. The first part deals with the equilibrium elastic response of a crosslinked rubberlike network. A simplified derivation will be given on the basis of the entropic approach. Some of the underlying assumptions will then be examined, and the contribution of internal energy to rubber elasticity scrutinized. The second part describes the transient viscoelastic properties of linear polymers in solution and in bulk. Limitations of the model will be assessed and its applications to experimental data explored. It should be pointed out that a number of reviews are available in the literature both for elasticity and viscoelasticity of polymers. The present work is not an exhaustive review of these fields, but rather concentrates on the more recent developments not previously discussed. The emphasis will be placed upon polymers in the bulk state, although solution properties will be mentioned where appropriate.

TREATISE ON EPDM

2012 ◽  
Vol 85 (3) ◽  
pp. 327-349 ◽  
Author(s):  
P. S. Ravishankar
Keyword(s):  
Technology Development ◽  
Polymer Chemistry ◽  
Metallocene Catalysts ◽  
Environmental Footprint ◽  
Process Technology ◽  
Technology Platforms ◽  
Recent Developments ◽  
Product Technology ◽  
Ziegler Natta Catalysts ◽  
Broad Overview

ABSTRACT EPDM is the designation given for a saturated polymer chain of the polymethylene type, consisting of ethylene, propylene, and diene. It has been and continues to be one of the most widely used and rapidly growing synthetic rubbers. Technology development has been driven by novel catalysts and processes that have expanded the range of products while delivering improvements in manufacturing such as energy efficiency and environmental footprint. A broad overview of the EPDM process and product technology is presented with focus on more recent developments. The range of topics includes polymer chemistry and physics, characterization, applications, and the manufacturing process. Technology platforms based on both the Ziegler–Natta catalysts and metallocene catalysts are compared and contrasted.

ChemInform Abstract: New Synthetic Methodology for Ring Expansion of n-Sized Conjugated Cycloalkenones into Homoallylic [n + 3] Lactones: Three-Step Synthesis of Fragrant Phoracantholide.

ChemInform ◽  
2001 ◽  
Vol 32 (10) ◽  
pp. no-no
Author(s):  
Gary H. Posner ◽  
Qiang Wang ◽  
Bethany A. Halford ◽  
Jeffrey S. Elias ◽  
John P. Maxwell
Keyword(s):  
Ring Expansion ◽  
Synthetic Methodology
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