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Synthesis, Structure and Reactivity of Cyclopenta-annulated 1,2,3,4-Tetrazines

Mackert, Peter J. ; Hafner, Klaus ; Nimmerfroh, Norbert ; Banert, Klaus (2023):
Synthesis, Structure and Reactivity of Cyclopenta-annulated 1,2,3,4-Tetrazines. (Publisher's Version)
In: Chemische Berichte, 127 (8), pp. 1479-1488. Wiley, e-ISSN 1099-0682,
DOI: 10.26083/tuprints-00022380,

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Chemische Berichte - August 1994 - Mackert - Synthesis Structure and Reactivity of Cyclopenta‐annulated 1 2 3 4‐Tetrazines.pdf
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Item Type: Article
Origin: Secondary publication service
Status: Publisher's Version
Title: Synthesis, Structure and Reactivity of Cyclopenta-annulated 1,2,3,4-Tetrazines
Language: English

The 2-aryl-2H-cyclopenta[e]-1,2,3,4-tetrazines 3a-n are formed by coupling of the diazocyclopentadienes 1a and 1b with arenediazonium salts and subsequent reversible electrocyclization of the primary coupling products 2a-n. From the solutions of the equilibrium mixtures of 2a ⇌ 3a - 2n ⇌ 3n the tetrazines 3a-d, h-k and the arylazo-diazocyclopentadienes 2e-g and 21-n crystallize. The 2-methyl-2H-cyclopenta[e]-1,2,3,4-tetrazines 3o and 3p are obtained by addition of methyllithium to 1a and 1b followed by a diazo transfer reaction and cyclization. In solutions of 3o and 3p the ring-opened isomers 2o and 2p could not be detected. X-ray analyses of 3h and 3p prove their bicyclic planar geometry in the solid state. ¹⁵N-NMR and temperature-dependent ¹H-NMR spectroscopy have enabled a detailed study of the reversible ring closure reaction in the case of 2d ⇌ 3d. Reaction of 2-phenyl-2H-cyclopenta[e]-1,2,3,4-tetrazine (3b) with tetrafluoroboric acid results in the formation of the protonated monocyclic salt 4. Furthermore 3b undergoes electrophilic substitution reactions preferably at C-7, as demonstrated by bromination, formylation, and trifluoroacetylation. Photolysis of solutions of 2i/3i, 2k/3k, and 21/31 leads to the ketene imines 11a-c. The structure of 11c has been determined by X-ray crystallography.

Journal or Publication Title: Chemische Berichte
Volume of the journal: 127
Issue Number: 8
Place of Publication: Darmstadt
Publisher: Wiley
Classification DDC: 500 Naturwissenschaften und Mathematik > 540 Chemie
Divisions: 07 Department of Chemistry > Organ Chemistry
Date Deposited: 20 Mar 2023 11:29
Last Modified: 20 Mar 2023 11:29
DOI: 10.26083/tuprints-00022380
Corresponding Links:
URN: urn:nbn:de:tuda-tuprints-223801
URI: https://tuprints.ulb.tu-darmstadt.de/id/eprint/22380
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