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5-Imino-1,4,5,6-tetrahydro-1,2,3,4-tetrazine aus 5-Alkyliden-4,5-dihydro-1H-tetrazolen und elektrophilen Aziden

✍ Scribed by Quast, Helmut ;Regnat, Dieter ;Balthasar, Jürgen ;Banert, Klaus ;Peters, Eva-Maria ;Peters, Karl ;Von Schnering, Hans Georg

Publisher
John Wiley and Sons
Year
1991
Tongue
English
Weight
745 KB
Volume
1991
Category
Article
ISSN
0947-3440

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✦ Synopsis

5‐Imino‐1,4,5,6‐tetrahydro‐1,2,3,4‐tetrazines Formed from 5‐Alkylidene‐4,5‐dihydro‐1__H__‐tetrazoles and Electrophilic Azides^1)^

The electrophilic azides 1 react with the 5‐alkylidenedihydrotetrazoles 8 already at low temperatures to produce high yields of the novel 5‐iminotetrahydro‐1,2,3,4‐tetrazines 10 besides molecular nitrogen. The configurations of (Z)‐10a, (E)‐10c, (Z)‐10d, and (E)‐10h are elucidated by means of X‐ray diffraction analyses. The formation of 10 is interpreted in terms of an initial [3 + 2] cycloaddition leading to the unstable spiro compounds 9. Ring opening of their dihydro‐1,2,3‐triazole ring generates the zwitterions 11 which lose molecular nitrogen with concomitant ring expansion of the dihydrotetrazole ring by a nitrogen 1,2‐shift. The tetrazines 10a–c and e are also obtained when 8a is generated from the tetrazolium salt 7a and trapped „in situ”︁ by the azides 1a–c and e.

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