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 -1 0 "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 (1 1 ), which was isolated as the dimer (1 2). Thermolysis of (3) in boiling toluene gave 6-amino-2,4-di-t-butylphenol (1 7), 2,4,6,8-tetra-t-butyl-I Hphenoxazin-I -one (21 ), and 2-cyano-9,9a-dihydro-3~5,7,9a-tetra-t-butylcyclopenta[6] [I ,4] benzoxazin-I (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 (1 7), (22), and (23) on thermolysis of the azide (3) is also discussed.It is well known that the decomposition of certain cyclic azides often results in ring expan~ion.~ It has been previously reported that 4-bromo-2,4,6-tri-tbutylcyclohexa-2,5-dienone (1) reacts with nucleophiles such as alcohol^,^ glycol^,^ sodium phenolates,6 and amines ' to afford the corresponding 4-substituted 2,4,6-tri-t-butylcyclohexa-2,5-dienones (2) in good yields. These results suggest that the reaction of the cyclohexadienone (1) with sodium azide may give 4-azido-2,4,6-tri-t-butylcyclohexa-2,5dienone (3).

Studies on Aerobic Reactions of Ammonia/3,5-Di-tert-butylcatechol Schiff-Base Condensation Products with Copper, Copper(I), and Copper(II). Strong Copper(II)−Radical Ferromagnetic Exchange and Observations on a Unique N−N Coupling Reaction

“…Quinones, and specifically 3,5-di- tert -butyl-1,2-benzoquinone, have been used in amine and amino acid deamination reactions, although, the formation of benzoxazole side-products is often a complication . Catechols undergo condensation with ammonia to give 2-aminophenols and bis(1-hydroxyphenyl)amines . Under oxidative conditions 2-aminophenoxyl radicals are formed that lead to cyclization with formation of phenoxazones, phenoxazines, and aminophenoxazinones in reactions that are often highly unselective …”

“…Catechols undergo condensation with ammonia to give 2-aminophenols and bis(1-hydroxyphenyl)amines . Under oxidative conditions 2-aminophenoxyl radicals are formed that lead to cyclization with formation of phenoxazones, phenoxazines, and aminophenoxazinones in reactions that are often highly unselective .…”

“…Further, in cases where the metal is present in stoichiometric concentrations, products may be obtained in the form of a metal complex. As a specific example, the condensation of ammonia with 3,5-DBCat under aerobic conditions proceeds to form a complicated series of cyclic and acyclic products, but in the presence of metal ion complexes of oxidized forms of bis(1-hydroxyphenyl)amine are obtained in relatively high yield. − The ligand that appears in these complexes may exist in several charged forms; the two most common forms have been identified as the Cat-N-BQ anion and Cat-N-SQ radical dianion ( I ) . With copper as the coordinating metal the course of the reaction is unusually dependent upon conditions.…”

Carbon‐ and SO2‐Locked Diarylnitroxides: Quantum Chemical Consideration, Synthesis, and Electrochemistry

“…The only exception is aforementioned Si and Ge‐containing biphenyl‐9,10‐dihydroacridin‐10‐yloxyl derivatives . The attempt to synthesize an oxygen‐locked diarylnitroxide has been reported but it was unsuccessful: corresponding phenoxazinyl radicals were formed instead of the nitroxide. Diarylnitroxides with sulfur‐containing bridge locking the ortho ‐positions of the phenyl rings have not been synthesized yet though their precursors (various phenothiazines) are well‐known and widely investigated (due to their application in luminescent materials, ).…”

Diarylamine/diarylnitroxide cycle: quantum chemical and electrochemical estimation

“…The latter has planar and rigid structure, contrary to the former one, in which rotation over the C–N bond is possible. According to the literature data, relatively stable aminyl radical was detected in aerobic oxidation of 2,4,6,8-tetra- tert -butylphenoxazine [17].…”