Limits...
Kinetic studies of inverse electron demand Diels-Alder reactions (iEDDA) of norbornenes and 3,6-dipyridin-2-yl-1,2,4,5-tetrazine.

Knall AC, Hollauf M, Slugovc C - Tetrahedron Lett. (2014)

Bottom Line: Norbornenes are, due to their straightforward synthetic availability, especially interesting in the latter context.Therefore, the reactivity of different norbornene-based compounds was compared with unsubstituted norbornene and other alkenes using UV-vis measurements for the determination of reaction rates under pseudo first order conditions.Thereby, exo,exo-5-norbornene-2,3-dimethanol was found to be almost as reactive as unsubstituted norbornene whereas (±)-endo,exo-dimethyl-5-norbornene-2,3-dicarboxylate reacted only insignificanty faster than unstrained alkenes.

View Article: PubMed Central - PubMed

Affiliation: Institute for Chemistry and Technology of Materials (ICTM), Graz University of Technology, Stremayrgasse 9, A-8010 Graz, Austria.

ABSTRACT
Inverse electron demand Diels-Alder additions (iEDDA) between 1,2,4,5-tetrazines and olefins have recently found widespread application as a novel 'click chemistry' scheme and as a mild technique for the modification of materials. Norbornenes are, due to their straightforward synthetic availability, especially interesting in the latter context. Therefore, the reactivity of different norbornene-based compounds was compared with unsubstituted norbornene and other alkenes using UV-vis measurements for the determination of reaction rates under pseudo first order conditions. Thereby, exo,exo-5-norbornene-2,3-dimethanol was found to be almost as reactive as unsubstituted norbornene whereas (±)-endo,exo-dimethyl-5-norbornene-2,3-dicarboxylate reacted only insignificanty faster than unstrained alkenes.

No MeSH data available.


Related in: MedlinePlus

1H NMR spectra of (a) 14, (b) after addition of pyTz, (c) after oxidation with DDQ (2,3-dichloro-5,6-dicyano-1,4-benzoquinone).
© Copyright Policy - CC BY
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4125744&req=5

f0015: 1H NMR spectra of (a) 14, (b) after addition of pyTz, (c) after oxidation with DDQ (2,3-dichloro-5,6-dicyano-1,4-benzoquinone).

Mentions: The 1H NMR spectrum of 14 (Fig. 3a) shows two olefinic double bonds, one at 5.2 ppm and one at 6 ppm. While the latter is consumed in the iEDDA reaction, the former notices a strong upfield shift (to approx. 5.8 ppm). Notably, the two adducts 18a/b (Fig. 3b) show significantly different chemical shifts which is most obvious for the NH signal of the dihydropyridazines (at 9.2 and 9.4 ppm) and the norbornene CH2 group (doublets, 1–1.8 ppm). After the oxidation, only one compound was found in the NMR spectrum, which could be assigned to 19 (Fig. 3c). While the two protons of the remaining double bond are split into two, more distinguished signals at 4.9 and 5.4 ppm, the signals corresponding to the bridgehead atoms experience a strong upfield shift (to 4.6, 3.7 and 3.2 ppm).


Kinetic studies of inverse electron demand Diels-Alder reactions (iEDDA) of norbornenes and 3,6-dipyridin-2-yl-1,2,4,5-tetrazine.

Knall AC, Hollauf M, Slugovc C - Tetrahedron Lett. (2014)

1H NMR spectra of (a) 14, (b) after addition of pyTz, (c) after oxidation with DDQ (2,3-dichloro-5,6-dicyano-1,4-benzoquinone).
© Copyright Policy - CC BY
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4125744&req=5

f0015: 1H NMR spectra of (a) 14, (b) after addition of pyTz, (c) after oxidation with DDQ (2,3-dichloro-5,6-dicyano-1,4-benzoquinone).
Mentions: The 1H NMR spectrum of 14 (Fig. 3a) shows two olefinic double bonds, one at 5.2 ppm and one at 6 ppm. While the latter is consumed in the iEDDA reaction, the former notices a strong upfield shift (to approx. 5.8 ppm). Notably, the two adducts 18a/b (Fig. 3b) show significantly different chemical shifts which is most obvious for the NH signal of the dihydropyridazines (at 9.2 and 9.4 ppm) and the norbornene CH2 group (doublets, 1–1.8 ppm). After the oxidation, only one compound was found in the NMR spectrum, which could be assigned to 19 (Fig. 3c). While the two protons of the remaining double bond are split into two, more distinguished signals at 4.9 and 5.4 ppm, the signals corresponding to the bridgehead atoms experience a strong upfield shift (to 4.6, 3.7 and 3.2 ppm).

Bottom Line: Norbornenes are, due to their straightforward synthetic availability, especially interesting in the latter context.Therefore, the reactivity of different norbornene-based compounds was compared with unsubstituted norbornene and other alkenes using UV-vis measurements for the determination of reaction rates under pseudo first order conditions.Thereby, exo,exo-5-norbornene-2,3-dimethanol was found to be almost as reactive as unsubstituted norbornene whereas (±)-endo,exo-dimethyl-5-norbornene-2,3-dicarboxylate reacted only insignificanty faster than unstrained alkenes.

View Article: PubMed Central - PubMed

Affiliation: Institute for Chemistry and Technology of Materials (ICTM), Graz University of Technology, Stremayrgasse 9, A-8010 Graz, Austria.

ABSTRACT
Inverse electron demand Diels-Alder additions (iEDDA) between 1,2,4,5-tetrazines and olefins have recently found widespread application as a novel 'click chemistry' scheme and as a mild technique for the modification of materials. Norbornenes are, due to their straightforward synthetic availability, especially interesting in the latter context. Therefore, the reactivity of different norbornene-based compounds was compared with unsubstituted norbornene and other alkenes using UV-vis measurements for the determination of reaction rates under pseudo first order conditions. Thereby, exo,exo-5-norbornene-2,3-dimethanol was found to be almost as reactive as unsubstituted norbornene whereas (±)-endo,exo-dimethyl-5-norbornene-2,3-dicarboxylate reacted only insignificanty faster than unstrained alkenes.

No MeSH data available.


Related in: MedlinePlus