Homogeneous Zinc(II) Catalysis in Accelerated Vulcanization III. Degradation Modes of Mono- and Disulfidic Cross-Links

1999 ◽  
Vol 72 (1) ◽  
pp. 27-42 ◽  
Author(s):  
P. J. Nieuwenhuizen ◽  
J. M. van Veen ◽  
J. G. Haasnoot ◽  
J. Reedijk
Keyword(s):  
Direct Evidence ◽  
Alder Reaction ◽  
Diels Alder ◽  
Molecular Processes ◽  
Cross Link ◽  
Hydride Shift ◽  
Diels Alder Reaction ◽  
New Information ◽  
Cross Links ◽  
First Time

Abstract This paper reports a Reaction-Stage-Modeling study dealing with degradation of mono- and disulfidic cross-links, providing new information about the molecular processes underlying the macrophysical phenomenon of reversion. The monosulfidic model cross-link (2,3-dimethyl-2-buten-1-yl)(2,3-dimethyl-1-buten-3-yl)sulfide was found to degrade at a relatively low temperature of 140 °C to yield olefins and α, β-unsaturated thioaldehydes. The latter species are not stable enough to be observed directly, but instead dimerize via an auto-Diels-Alder reaction to give a—fully-characterized—1,3-dithiin. The disulfidic model cross-link bis(2,3-dimethyl-2-buten-1-yl)disulfide was observed to degrade according to a previously unknown mechanism, involving a 1,4-hydride shift, to furnish a 1,3-dipolar intermediate. The reaction is catalyzed by bis(diethyldithiocarbamato)zinc(II), ZDEC, and the activation enthalpy ΔH‡ of the reaction has been determined to be ∼ 71(7) kJ mol− . Several dienophiles and dipolarophiles were applied to trap the α, β-unsaturated thioaldehyde and 1,3-dipolar intermediate, but neither was successful. Overall, this study has furnished direct evidence for degradation of mono- and disulfidic cross-links via hydrogen shifts and indicates, for the first time, in what way zinc complexes may cause cross-link degradation and induce reversion in rubber vulcanizates.

Ring-Closing Metathesis Approach to Cage Propellanes Containing Oxepane and Tetrahydrofuran Hybrid System

Synthesis ◽  
2017 ◽  
Vol 49 (24) ◽  
pp. 5339-5350 ◽  
Author(s):  
Sambasivarao Kotha ◽  
Subba Cheekatla ◽  
Darshan Mhatre
Keyword(s):  
Claisen Rearrangement ◽  
Alder Reaction ◽  
Diels Alder ◽  
Ring Closing Metathesis ◽  
Cage Compounds ◽  
Transannular Cyclization ◽  
Diels Alder Reaction ◽  
Grignard Addition ◽  
Key Steps ◽  
First Time

The preparation of a variety of structurally interesting oxygenated cage compounds involving atom-economic processes such as Claisen rearrangement, Diels–Alder reaction, [2+2] photocycloaddition, and ring-closing metathesis (RCM) as key steps is reported. For the first time, oxepane ring system is introduced in cage framework using olefin metathesis as a key step. These cage systems assembled here are difficult to prepare by traditional methods. The synthetic sequence described here opens up new routes to higher order polycycles containing heteroatoms without the involvement of protecting groups. Transannular cyclization observed during Grignard addition and the RCM protocol used here may be applicable to generate unknown oxygenated cage systems.

Interplay between crystallization and the Diels–Alder reaction in biobased multiblock copolyesters possessing dynamic covalent bonds

2017 ◽  
Vol 8 (29) ◽  
pp. 4280-4289 ◽  
Author(s):  
Yang Zhang ◽  
Zehui Dai ◽  
Jiarui Han ◽  
Ting Li ◽  
Jun Xu ◽  
...  
Keyword(s):  
Alder Reaction ◽  
Diels Alder ◽  
Covalent Bonds ◽  
Diels Alder Reaction ◽  
Cross Links

Biobased multiblock copolyesters possessing physical cross-links via crystallization and chemical cross-links via the Diels–Alder reaction at the same time.

Gold-Catalyzed [1,5]-Hydride Shift onto Unactivated Alkynes To Trigger an Intermolecular Diels–Alder Reaction

2014 ◽  
Vol 16 (14) ◽  
pp. 3820-3823 ◽  
Author(s):  
Xiang Wu ◽  
Shu-Sen Chen ◽  
Yue Hu ◽  
Liu-Zhu Gong
Keyword(s):  
Alder Reaction ◽  
Diels Alder ◽  
Hydride Shift ◽  
Diels Alder Reaction

A new route for the synthesis of highly substituted 4-aminoquinoline drug like molecules via aza hetero–Diels–Alder reaction

2015 ◽  
Vol 13 (28) ◽  
pp. 7614-7618 ◽  
Author(s):  
Shinde Vidyacharan ◽  
A. Sagar ◽  
Duddu S. Sharada
Keyword(s):  
Alder Reaction ◽  
Diels Alder ◽  
Diels Alder Reaction ◽  
First Time

A new route has been developed for the synthesis of 4-aminoquinoline drug like moleculesviaaza hetero–Diels–Alder reaction starting from 2H-indazole as a diene for the first time.

Two-dimensional Raman correlation spectroscopy reveals molecular structural changes during temperature-induced self-healing in polymers based on the Diels–Alder reaction

2015 ◽  
Vol 17 (35) ◽  
pp. 22587-22595 ◽  
Author(s):  
R. Geitner ◽  
J. Kötteritzsch ◽  
M. Siegmann ◽  
T. W. Bocklitz ◽  
M. D. Hager ◽  
...  
Keyword(s):  
Correlation Analysis ◽  
Structural Changes ◽  
Alder Reaction ◽  
Diels Alder ◽  
Correlation Spectroscopy ◽  
Self Healing ◽  
Two Dimensional ◽  
Diels Alder Reaction ◽  
First Time ◽  
Raman Correlation Spectroscopy

For the first time two-dimensional Raman correlation analysis has been used to study self-healing polymers based on the Diels–Alder reaction.

scholarly journals Thiourea-catalyzed Diels–Alder reaction of a naphthoquinone monoketal dienophile

2013 ◽  
Vol 9 ◽  
pp. 1414-1418 ◽  
Author(s):  
Carsten S Kramer ◽  
Stefan Bräse
Keyword(s):  
Natural Products ◽  
Total Synthesis ◽  
Alder Reaction ◽  
Diels Alder ◽  
Selective Synthesis ◽  
Quaternary Center ◽  
Diels Alder Reaction ◽  
Cycloaddition Product ◽  
Sterically Hindered ◽  
First Time

A variety of organocatalysts were screened for the catalysis of the naphthoquinone monoketal Diels–Alder reaction. In this study we found that Schreiner's thiourea catalyst 10 and Jacobson's thiourea catalyst 12 facilitate the cycloaddition of the sterically hindered naphthoquinone monoketal dienophile 3 with diene 4. The use of thiourea catalysis allowed for the first time the highly selective synthesis of the exo-product 2a in up to 63% yield. In this reaction a new quaternary center was built. The so formed cycloaddition product 2a represents the ABC tricycle of beticolin 0 (1) and is also a valuable model substrate for the total synthesis of related natural products.

First Direct Evidence in Biological Diels-Alder Reaction of Incorporation of Diene-Dienophile Precursors in the Biosynthesis of Solanapyrones

1994 ◽  
Vol 116 (8) ◽  
pp. 3605-3606 ◽  
Author(s):  
Hideaki Oikawa ◽  
Yuichi Suzuki ◽  
Akira Naya ◽  
Kinya Katayama ◽  
Akitami Ichihara
Keyword(s):  
Direct Evidence ◽  
Alder Reaction ◽  
Diels Alder ◽  
Diels Alder Reaction

Imino Diels–Alder reaction — An efficient synthetic protocol for 2-methyl-4-substituted tetrahydroquinolines catalyzed by copper dipyridine dichloride

2010 ◽  
Vol 88 (5) ◽  
pp. 443-452 ◽  
Author(s):  
C. S. Kavitha ◽  
K. M. Hosamani ◽  
R. S. Harisha
Keyword(s):  
Elemental Analysis ◽  
Alder Reaction ◽  
Diels Alder ◽  
Reusable Catalyst ◽  
Substituted Anilines ◽  
H Nmr ◽  
Diels Alder Reaction ◽  
First Time ◽  
C Nmr

For the first time, copper dipyridine dichloride (CuPy2Cl2) is used as an efficient and reusable catalyst for the imino Diels–Alder reaction of para-substituted anilines with N-vinylpyrrolidinone, N-vinylcarbazole, and N-vinylcaprolactam in acetonitrile to afford the corresponding 2-methyl-4-substituted-1,2,3,4-tetrahydroquinoline derivatives in excellent yields with good purity. The products were characterized by FTIR, 1H NMR, 13C NMR, MS, and elemental analysis.

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