Flash vacuum pyrolysis of azolylacroleins and azolylbutadienes

• Published in: Tetrahedron Vol. 68; no. 4; pp. 1299 - 1305
• Main Authors: Lucero, Paola L., Peláez, Walter J., Riedl, Zsuzsanna, Hajós, György, Moyano, Elizabeth L., Yranzo, Gloria I.
• Format: Journal Article
• Language: English
• Published: OXFORD Elsevier Ltd 28.01.2012; Elsevier
• Subjects: Butadiene; Carbenes; Chemistry; Chemistry, Organic; Derivatives; Exact sciences and technology; Extrusion; Formations; Free radicals chemistry; Heterocyclic compounds; Heterocyclic compounds with only one n hetero atom and condensed derivatives; Heterocyclic compounds with several n hetero atoms in the same ring, in separated rings or in fused rings; Indazole; Mathematical analysis; Nitrilimine; Nitrogen extrusion; Noncondensed benzenic compounds; Organic chemistry; Physical Sciences; Preparations and properties; Pyrolysis; Reactivity and mechanisms; Science & Technology; Tetrahedrons; Tetrazole; Pyrolysis; Nitrilimine; Nitrogen extrusion; Tetrazole; Indazole; THERMOLYSIS; INTRAMOLECULAR CYCLIZATION; CARBENE REARRANGEMENTS; CONVERSION; NITRILE IMINES; SALTS; NITRILIMINES; Tetrazole derivatives; Under vacuum; Nitrogen heterocycle; Azole derivatives; Flash pyrolysis; Thermal reaction; Fragmentation; Acrolein; Carbene; 1,2,3-Triazole derivative; Chlorine Organic compounds; Aromatic compound; Theoretical study; Aniline derivatives; Indazole derivatives; Butadiene derivatives; Cyclization; Organic free biradical; Density functional method; Benzenic compound
• ISSN: 0040-4020; 1464-5416
• DOI: 10.1016/j.tet.2011.11.034

2-Aryl-5-acroleinyl-1,2,3,4-tetrazoles ( 1a– d) and 2-aryl-5-butadienyl-1,2,3,4-tetrazoles ( 1e– g) were subjected to flash vacuum pyrolysis. Acroleinyl derivatives resulted in nitrogen extrusion to give nitrilimines followed by ring closure to give the corresponding indazoles 3a– d 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. [Display omitted]