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5‐Imino‐1,4,5,6‐tetrahydro‐1,2,3,4‐tetrazine aus 5‐Alkyliden‐4,5‐dihydro‐1 H ‐tetrazolen und elektrophilen Aziden
Author(s) -
Quast Helmut,
Regnat Dieter,
Balthasar Jürgen,
Banert Klaus,
Peters EvaMaria,
Peters Karl,
Von Schnering Hans Georg
Publication year - 1991
Publication title -
liebigs annalen der chemie
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 0170-2041
DOI - 10.1002/jlac.199119910176
Subject(s) - chemistry , tetrazine , ring (chemistry) , electrophile , cycloaddition , nitrogen , azide , triazole , medicinal chemistry , stereochemistry , organic chemistry , catalysis
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 .