Unexpected valence bond isomerization of [1,2,4]triazolo[3,4-c][1,2,4]benzotriazines under flash vacuum pyrolytic (fvp) conditions |
| |
Authors: | Walter J Peláez Csilla Gróf György Hajós |
| |
Institution: | a INFIQC-Depto. de Química Orgánica, Facultad de Ciencias Químicas, U.N.C. Córdoba, Argentina b Chemical Research Center, Institute of Biomolecular Chemistry, Hungarian Academy of Sciences, Pusztaszeri út 59-67, H-1025 Budapest, Hungary |
| |
Abstract: | Flash vacuum pyrolysis (fvp) of some substituted 1,2,4]triazolo3,4-c]1,2,4]benzotriazine derivatives (1a-d) has been studied between 450 and 600 °C. The only transformation observed up to 525 °C was the unexpected valence bond isomerization of the angularly fused starting compounds to the isomeric linearly fused 1,2,4]triazolo4,3-b]1,2,4]benzotriazine derivatives (9a-d), whereas at higher temperatures fragmentation products such as aromatic nitriles were also formed. Kinetic measurements revealed negative entropies of activation in the isomerization process, which suggest a concerted ring closure reaction to an intermediate antiaromatic diazirine. Reversibiblity of the title isomerization reaction was also proved by FVP experiments. |
| |
Keywords: | Flash vacuum pyrolysis Valence bond isomerisation Sigmatropic rearrangement Enthropy of activation Azirine intermediate |
本文献已被 ScienceDirect 等数据库收录! |
|