1,2,4,5‐Tetrazin‐1(2H)‐yl‐Radikale

Abstract

1,2,4,5-Tetrazin-l(ZH)-yl-Radikale(2) lassen sich durch Dehydrierung entsprechender 1,4-Dihydro-l,2,4,5-tetrazine (6) mit Bis(4-methylpheny1)aminyl erzeugen. Die Konstitution dieser neuartigen persistenten Radikale wurde durch ESR-spektroskopische Untersuchung markierter Derivate gesichert.1,2,4,5-Tetrazin-l(2H)-yl Radicals 1,2,4,5-Tetrazin-l(2H)-yl radicals (2) can be generated by dehydrogenation of corresponding 1,4-dihydro-l,2,4,5-tetrazines (6) with bis(4-methylpheny1)aminyl. The structure of these new persistent radicals was confirmed by ESR studies of labelled derivatives.Zwischen dem 1,2,4,5-Tetrazin-RadikaIanion (1) und dem 1 ,4-Dihydro-l,2,4,5-tetrazin-Radikalkation (3a) laBt sich als erste Protonierungsstufe ein ungeladenes 1,2,4,5-Tetrazin-1(2H)-yl-Radikal (2a) formulieren, das strukturelle Parallelen zu Verdazylen (z. B. 4) aufweist. Bei beiden Radikaltypen handelt es sich um ,,7-~-Elektronen"-l,2,4,5-Tetrazin-Derivate, die als charakteristisches Strukturelement eine Hydrazyl-Funktion enthalten. Die Radikalionen 1 und 3 a und insbesondere zahlreiche substituierte Vertreter sind ESR-spektroskopisch eingehend untersucht worden' -9). Uber die Eigenschaften der Neutralradikale vom Typ 2 dagegen ist, wenn man von Radikalen der Konstitution 5 absieht, bisher offenbar nichts bekannt.Im Zusammenhang rnit Arbeiten uber Dihydrotetrazine" beobachteten wir, daJ3 1 ,4-Dihydro-l-methyl-3,6-diphenyl-l,2,4,5-tetrazin (6c) bei der Umsetzung mit Bis-(4-methylpheny1)aminyl (BMA; erzeugt durch photolytische Dissoziation des entspre-Chem.

Nucleophilic Attack on Nitrogen in Tetrazines by Silyl-Enol Ethers

“…[14,15] To the best of our knowledge, there are only three reports in the literature on the addition of hard organometallic reagents, such as RLi or RMgX, to the tetrazine core. [14,16,17] Neugebauer and Siegel were first to react unsubstituted s-tetrazine with methyl magnesium iodide to give 1,4-dihydro-1-methyl-s-tetrazine, [17] which was corroborated independently at the same time by…”

Verdazyls and Related Radicals Containing the Hydrazyl [R2N‐NR] Group

“…162 The low symmetry of their structure leads to rather complex EPR spectra, but a combination of isotopically enriched derivatives ( 2 H, 15 N) permitted full assignment of all of the nitrogen and proton hyperfine coupling constants. The spin density distribution picture which emerges (Figure 7.6) is qualitatively not unlike that of the verdazyl radical system.…”

Glycosylidene Carbenes. Part 31

“…15 ) The 1,4-dihydro-1,2,4,5-tetrazines adopt a flattened 3,6 B conformation with the 3-and 6-substituents in bowsprit position [32]. A 1,2-dihydro-1,2,4,5-tetrazine structure is excluded, since 1,2-dihydro-1,2,4,5tetrazines rearrange readily to the more-stable 1,4-dihydro-1,2,4,5-tetrazines [33]. 16 ) For the reaction of hexono-1,5-lactone hydrazone to a 4-amino-4H-1,2,4-triazole and a 1,2,4,5-tetrazine via a 1,2-dihydro-1,2,4,5-tetrazine, see [37].…”