Flash vacuum pyrolysis of azolylacroleins and azolylbutadienes

PAOLA LUCERO; WALTER PELÁEZ; ZSUZANNE RIEDL; GYORGY HAJOS; ELIZABETH MOYANO; GLORIA YRANZO

TETRAHEDRON

PERGAMON-ELSEVIER SCIENCE LTD

Lugar: Amsterdam; Año: 2012 vol. 68 p. 1299 - 1305

0040-4020

2-Aryl-5-acroleinyl-1,2,3,4-tetrazoles (1aed) and 2-aryl-5-butadienyl-1,2,3,4-tetrazoles (1eeg) weresubjected to flash vacuum pyrolysis. Acroleinyl derivatives resulted in nitrogen extrusion to give nitrilimines followed by ring closure to give the corresponding indazoles 3aed in good yields. On the other hand, butadiene derivatives underwent ring fragmentation to give p-substituted anilines without formation of the expected indazoles. Differences between thermal behaviour of 2-(4-chlorophenyl)-5-acroleinyl-1,2,3,4-tetrazole (1c) and 1-(4-chlorophenyl)-4-acroleinyl-1,2,3-triazole (2) were studied in details. DFT calculations have been used to examine the nitrilimine and carbene nature of the intermediates involved in the thermal reactions of azolyl derivatives.