scholarly journals New insights into the cross-linking and degradation mechanism of Diels–Alder hydrogels

2015 ◽  
Vol 3 (3) ◽  
pp. 449-457 ◽  
Author(s):  
Susanne Kirchhof ◽  
Andrea Strasser ◽  
Hans-Joachim Wittmann ◽  
Viktoria Messmann ◽  
Nadine Hammer ◽  
...  
Keyword(s):  
Ring Opening ◽  
Degradation Mechanism ◽  
Alder Reaction ◽  
Diels Alder ◽  
Cross Linking ◽  
Diels Alder Reaction ◽  
Maleamic Acid ◽  
The Cross ◽  
Hydrolysis Of

Degradation of Diels–Alder hydrogels occurs by retro-Diels–Alder reaction followed by OH−-catalyzed ring-opening hydrolysis of maleimide groups to unreactive maleamic acid derivatives.

scholarly journals Towards Thermally Reversible Networks Based on Furan-Functionalization of Jatropha Oil

Molecules ◽  
2020 ◽  
Vol 25 (16) ◽  
pp. 3641
Author(s):  
Frita Yuliati ◽  
Peter J. Deuss ◽  
Hero J. Heeres ◽  
Francesco Picchioni
Keyword(s):  
Ring Opening ◽  
Alder Reaction ◽  
Diels Alder ◽  
Epoxide Ring ◽  
Cross Linking ◽  
Jatropha Oil ◽  
Optimum Conditions ◽  
Epoxide Ring Opening ◽  
Diels Alder Reaction ◽  
Ring Opening Reaction

A novel biobased monomer for the preparation of thermally reversible networks based on the Diels-Alder reaction was synthesized from jatropha oil. The oil was epoxidized and subsequently reacted with furfurylamine to attach furan groups via an epoxide ring opening reaction. However, furfurylamine also reacted with the ester groups of the triglycerides via aminolysis, thus resulting in short-chain molecules that ultimately yielded brittle thermally reversible polymers upon cross-linking via a Diels-Alder reaction. A full-factorial experimental design was used in finding the optimum conditions to minimize ester aminolysis and to maximize the epoxide ring opening reaction as well as the number of furans attached to the modified oil. The optimum conditions were determined experimentally and were found to be 80 °C, 24 h, 1:1 molar ratio, with 50 mol % of LiBr with respect to the modified oil, resulting in 35% of ester conversion, 99% of epoxide conversion, and an average of 1.32 furans/triglyceride. Ultimately, further optimization by a statistical approach led to an average of 2.19 furans per triglyceride, which eventually yielded a flexible network upon cross-linking via a Diels-Alder reaction instead of the brittle one obtained when the furan-functionalization reaction was not optimized.

A synthesis and some reactions of 7-Oxabicyclo[2.2.1]heptan-2-one

1983 ◽  
Vol 36 (12) ◽  
pp. 2473 ◽  
Author(s):  
J Moursounidis ◽  
D Wege
Keyword(s):  
Thermal Decomposition ◽  
Alder Reaction ◽  
Diels Alder ◽  
Acid Mixture ◽  
Diels Alder Reaction ◽  
Reaction Proceeds ◽  
Atom Migration ◽  
Acyl Azide ◽  
Mild Hydrolysis ◽  
Hydrolysis Of

Diels-Alder reaction between furan and α-chloroacrylonitrile gives a mixture of exo-2-chloro-and endo-2-chloro-7-oxabicyclo[2.2.1]hept-5-ene-2-carbonitrile (4) and (5). Mild hydrolysis affords the corresponding α-chloro acid mixture, from which the endo carboxylic acid may be removed through iodo lactone formation. Catalytic hydrogenation of (4) and (5) followed by hydrolysis, acyl azide formation, Curtius rearrangement, and hydrolysis of the resulting mixture of a-chloro isocyanates yields 7-oxabicyclo[2.2.l]heptan-2-one (1) in preparatively useful amounts. Reduction of (1) gives only endo alcohol, and Baeyer-Villiger reaction proceeds with exclusive bridgehead atom migration. Thermal decomposition of the sodium salt of the p-toluenesulfonylhydrazone of (1) affords 7-oxatricyclo[2.2.1 .02,6]heptane.

scholarly journals Imidazolinium and amidinium salts as Lewis acid organocatalysts

2012 ◽  
Vol 8 ◽  
pp. 1798-1803 ◽  
Author(s):  
Oksana Sereda ◽  
Nicole Clemens ◽  
Tatjana Heckel ◽  
René Wilhelm
Keyword(s):  
Lewis Acid ◽  
Ring Opening ◽  
Alder Reaction ◽  
Diels Alder ◽  
Diels Alder Reaction

The application of imidazolinium and amidinium salts as soft Lewis acid organocatalysts is described. These salts were suitable catalysts for the activation of unsaturated thioesters in a Diels–Alder reaction and in the ring opening of thiiranes and epoxides. The products were isolated in good yields. The mild catalysts did not cause desulfurization of the products containing a thiol or thiocarbonyl group.

scholarly journals Direct Diels-Alder reaction of chitin derived 3-acetamido-5-acetylfuran

2022 ◽  
Author(s):  
Rafael Gomes ◽  
Juliana Pereira ◽  
João Ravasco ◽  
João Vale ◽  
Fausto Queda
Keyword(s):  
Alder Reaction ◽  
Diels Alder ◽  
Fine Tuning ◽  
Reduced Form ◽  
Partial Hydrolysis ◽  
Reaction Conditions ◽  
Diels Alder Reaction ◽  
Direct Use ◽  
Kinetics Of ◽  
Hydrolysis Of

The Diels-Alder (DA) reaction of biomass derived furans is an emerging technology for the preparation of new molecular entities and “drop-in” commodity chemicals. In this work we address the challenge of the direct use of electron-poor furanic platforms as dienes through the use of an unexplored chitin derived furan, 3-acetamido-5-acetylfuran (3A5AF). The 3-acetamido group promoted a remarkable increase in the kinetics of the DA allowing for the preparation of 7-oxanorbornenes (7-ONB) at 50 ºC. Partial hydrolysis of the enamide to hemi-acylaminals was possible upon fine tuning of the reaction conditions, disabling retro-DA processes. Finally, DA reaction of the reduced form of 3A5AF allowed quantitative formation of 7-ONB in aqueous condition after 10 minutes. Certanly these are the first steps for expanding the toolbox of chitin derived 3A5AF as diene.

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