Occurrence of the SN(ANRORC) Mechanism in the Hydrazination of 1,2,4,5-Tetrazines

Article abstract of DOI:10.1021/jo00338a009

3-Alkyl(aryl)-1,2,4,5-tetrazines (7) when treated with hydrazine hydrate were found to undergo a Chichibabin hydrazination into 3-alkyl(aryl)-6-hydrazino-1,2,4,5-tetrazines (8) according to an S_N(ANRORC) mechanism. 1H and 13C NMR measurements indicate that the first step in this reaction sequence is the formation of a homoaromatic ? adduct anion, due to attack at C6, and that the second step is the formation of an open-chain intermediate.With 15N-labeled hydrazine, part of the label is found in the 1,2,4,5-tetrazine ring of the 6-hydrazino compounds 8*.NMR evidence is obtained which shows that the hydrazino compounds with ¹⁵N-label in the ring (8^*II) and with the ¹⁵N-label in the hydrazino group (8^*I) are formed according to the S_N(ANRORC) mechanism.Treatment of 6-amino- or 6-halogeno-1,2,4,5-tetrazines with hydrazine leads to introducing of a hydrazino group at position 6.During this hydrazino deamination and hydrazino dehalogenation part of the molecules were found to react according to the S_N(ANRORC) mechanism, the other part followed the S_N(AE) pathway.