Hetaryl-substituted dienamines (1a–c and 4a–c) of different geometry when treated with dimethyl 1, 2,4, 5-tetrazine-3, 6-dicarboxylate (2) reacted selectively as enamines (i.e. with the Δ3, 4 double bond) to afford the appropriate E or Z (hetarylvinyl)pyridazines (i.e. 1a–c gave 3a–c, whereas 4a–c afforded 5a–c). Study on the analogous transformation of the 1Z diene ether (6a) revealed that, in apolar solvent, isomerization of the olefinic side chain occurred (3a rather than 5a was obtained). Formation of the trans product 3a was rationalized by a tautomeric equilibrium of the supposed intermediate 7 for which experimental evidence was provided.
ASJC Scopus subject areas
- Organic Chemistry