Cyclodienones. Part 6. Preparation of 4-azido-2,4,6-tri-t-butyl-cyclohexa-2,5-dienone and its thermal, photo-, and acid-catalyzed decomposition

Abstract

Preparation of 4-azido-2,4,6-tri-t-butylcyclohexa-2,5-dienone (3) from 4-bromo-2,4,6-tri-t-butylcyclohexa-2,5-dienone (1) and sodium azide is described. Treatment of (3) with concentrated sulphuric acid afforded 2,6-di-t-butyl-p-benzoquinone (7) in 75% yield, while the reaction at –10 °C in chloroform solution gave a tri-t-butylazepinone (5) and 3,5-di-t-butyl-o-benzoquinone (8). Photolysis of (3) in benzene afforded 2,4-di-t-butylcyclopenta-2,4-dienone (11), which was isolated as the dimer (12). Thermolysis of (3) in boiling toluene gave 6-amino-2,4-di-t-butylphenol (17), 2,4,6,8-tetra-t-butyl-1H-phenoxazin-1-one (21), and 2-cyano-9,9a-dihydro-3,5,7,9a-tetra-t-butylcyclopenta[b][1,4]benzoxazin-1(3aH)-one (22) in 15,15 and 48% yields, respectively. When the thermolysis was carried out with very low reagent concentrations, 5-cyano-2,4-di-t-butylcyclopenta-2,4-dienone (23), in addition to the phenol (17), was obtained. The compound (23) was also obtained by thermolysis of (3) in boiling acetic anhydride and in boiling toluene containing acetic anhydride. The reaction pathway for the formation of compounds (17), (22), and (23) on thermolysis of the azide (3) is also discussed.