Benzene, decomposition azides

The rate of decomposition of benzenesulphonyl azide to benzene-sulphonamide is said to be accelerated appreciably by thiophenol 18> in a radical-catalyzed process probably not involving a free nitrene intermediate. 

Copper catalyzes the decomposition of sulphonyl azides in benzene very slowly. When methanesulphonyl azide was boiled under reflux in benzene solution in the presence of an excess of freshly reduced copper powder, some decomposition occurred to give methanesulphonamide and azide was recovered 78>. Transition metal complexes have been found to exert a marked effect upon the yields of products and isomer ratios formed in the thermal decomposition of methanesulphonyl azide in methyl benzoate and in benzotrifluoride 36>. These results will be discussed in detail in the section on the properties of sulphonyl nitrenes and singlet and triplet behaviour. A sulphonyl nitrene-iron complex has recently been isolated 37> and more on this species will be reported soon. 

Starting materials other than sulphonyl azides have been used as possible sources of sulphonyl nitrenes. The decomposition of the triethyl-ammonium salt of iV- -nitrobenzenesulphonoxybenzenesulphonamide (26) in methanol, ethanol, and aniline gave products derived from a Lossen-type rearrangement 20> (Scheme 3). It was felt that the rearrangement did not involve a free sulphonyl nitrene since, when the decomposition was carried out in toluene-methylene chloride or in benzene, no products (benzenesulphonamides) of substitution of the aromatic solvent nucleus were found (as are usually found with sulphonyl nitrenes from the thermal decomposition of the corresponding azides). On the other... 

The thermal, but not the photochemical, decomposition of ferro-cenylsulphonyl azide (14) in benzene gave some intermolecular aromatic substitution product FCSO2NHC6H5 (6.5%) but no intermolecular cyclization product (17). Contrariwise, photolysis of 14 in benzene gave 17 but no anilide 1 ). 

It is important that the water be removed as completely as possible before the azide is added to the warm benzene. Failure to remove the water causes formation of the ijm.-disubstituted urea during decomposition of the azide. If the water is separated carefully, there will be no need to filter the benzene solution before the final distillation. 

Although anation and aquation rates of vitamin B12 are not affected appreciably by aqueous micelles, the solubilized water in reversed micelles, in contrast, influences the rate and equilibrium constants for the formation and decomposition of glycine, imidazole, and sodium azide adducts of vitamin Bl2 (Fendler et al., 1974). A vitamin B12 molecule is conceivably shielded from the apolar solvent (benzene) by some 300 surfactant molecules. 

Coleman, Newman, and Garrett have kinetically investigated the decomposition of benzoyl azide in benzene and nitrobenzene solution with halides as Lewis adds.1 7 They grouped the halides into three classes based on the kinetic equation involved ... 

Kwart and Kahn have found that benzenesulfonyl azide forms a complex with freshly reduced copper powder.189 190 This copper azide complex decomposes at a lower temperature than the pure sulfonyl azide. In refluxing methanol, benzene-sulfonamide (27) is isolated as the major product. In the presence of dimethyl sulfoxide, N-benzenesulfonyldimethyl-sulfoximine (28) is obtained in almost quantitative yield. In cyclohexene solution benzenesulfonamide (29), N-benzenesul-fonyl-7-azabicyclo[4.1.0]heptane (30), and 1-cyclohexenylben-zenesulfonamide (31) are isolated as the main reaction products. According to the authors, Schemes VII and VIII represent an acceptable interpretation of the experimental data.189 190 In pure alcohol, the decomposition should occur by two competitive reactions (Scheme VII) producing benzenesulfonamide together with a ketone and oxidized copper. These last two products have indeed been observed in the reaction mixture. In the presence of DMSO, it seems that a copper-nitrene intermediate is formed which is trapped by DMSO. In cyclohexene solution, the authors have observed that the aziridine (30) disappears from the product composition when DMSO is added. The yield of enamine 31, however, is... 

Carbohydrazide is a white crystalline compound melting with decomposition at 153 to 154°. It is very soluble in water but insoluble in alcohol, ether, chloroform, and benzene. It reacts with benzaldehyde to form dibenzalcar-bohydrazide, 0=C(NHN"=CHC6H5)2, which melts at 1980.6 In the presence of nitrous acid, carbohydrazide is converted into carbonyl azide, CO (Ns) 2, a highly explosive compound.3... 

Hexazine has constituted an intriguing fictitious molecule. It was studied theoretically in order to understand why it cannot be observed experimentally. Glukhovtsev and Schleyer concluded that among Ne possible isomers, hexazine is less stable than a twist open-chain dimer of two azide radicals with C2 symmetry (which, however, is thermodynamically unstable relative to the exothermal decomposition into 3N2 releasing 188.3 kcal/mol). In marked contrast to benzene, hexazine is calculated to be non-planar due to lone-pair repulsion into the cr system. Homodesmotic reactions ... 

Other aminoferrocene precursors are Af-ferrocenyl phthalimide, which can be converted to FC-NH2 by N2H4 H2O in boiling ethanol (82% yield) [16, 44], and ferrocenyl azide, FC-N3, which has been reduced with LiAlH4 (72% yield) (cf. Scheme 5-6) [45]. Ferrocenyl amine, FC-NH2, is generally formed among other products in the thermal or photochemical decomposition of FC-N3 [56] and in the thermolysis of ferrocenyl isocyanate, Fc-NCO [57], in solvents such as cyclohexane, cyclohexene and benzene, probably by reaction of the intermediate nitrene, [Fc-N], with the solvent [56, 57]. The reduction of nitroferrocene, FC-NO2, provides another route to aminoferrocene, FC-NH2 [58 — 61] however, FC-NO2 is not an easily accessible starting material. 

The decomposition is first order in nitrobenzene and tetrahydronaphthalene and the Arrhenius parameters obtained with various solvents for phenyl azide and some derivatives are collected in Table 16. As seen from the data, meta substitution has no efiect on the rate, and it was concluded that the rate-determining step is N2 evolution and not ring closure to form azepines (in aniline solution). In indene, Smith observed that para substituents increased the rate of Nj evolution by about eight times however, with both meta and para substituents the amine yields varied widely and in some cases the Nj yields were not quantitative with respect to the amount of azide decomposed. Benzenes and substituted benzenes have been observed in small amounts and it appears that a minor decomposition pathway would involve azide radical loss . On the other hand, Waters reports that the thermolysis of phenyl azides proceeds by different mechanisms, depending on the medium ... 

There has been one report of an acid-catalysed decomposition of sulphonyl azides ". In the presence of aromatic substrates and sulphuric acid below 25° arylsulphonyl azides caused amination of the aromatic substrate. For example, benzenesulphonyl azide gave aniline (60-65%), benzenesulphonic acid and nitrogen when treated with sulphuric acid in the presence of benzene. Similar decompositions in toluene or chlorobenzene led to o- and p- substituted anilines... 

Decomposition of aUcyl azides with aluminium chloride in benzene at 50° gave products which corresponded to the formation of a carbonium ion (loss of N3 ) and to an electron-deficient nitrogen (loss of N2) . For example, cyclohexyl azide gave phenylcyclohexane (30%), cyclohexanone imine (90) (15%) and the ring-expanded imine (91) (30-40%). The same workers reported the first example of an aUcyl nitrenium ion being trapped by benzene in reasonable yieldIn the presence of three equivalents of aluminium chloride in benzene, azidoacetone (92) gave the aromatic substitution product (93) in 35%... 

Bertho first studied the decomposition of phenyl azide in benzene and /i-xylene. He found that when the decomposition was carried out in benzene under pressure at 150-160° for 7-8 hours, azobenzene (11%) and aniline (18%) were obtained. When the reaction wzis carried in -xylene under the same conditions, aniline (85%), a small amount of azobenzene, and, -ditolylethane were obtained. 

The thermal decomposition of ferrocenyl azide in benzene gave ferrocene (13 6%), phenylferrocene (1 9%), azoferrocene (17 8%), and ferroccnylamine (16-9%) Thermolysis of this azide in cyclohexane gave ferrocene (7 3%), and azoferrocene (20 5%). No product of aliphatic G—H insertion nor of aromatic substitution by the nitrene was observed (For more results and a comparison with photolysis, see section V.B.). 

Thermolysis of benzoyl peroxide in a degassed solution of phenyl azide in benzene at 80° led to no decomposition of the azide over two... 

Decomposition of methanesulphonyl azide in a mixture of benzene and substituted benzene resulted in the following total rate ratios for sulphonamidation anisole, 2 54 toluene, 1-86 and chlorobenzene, 0-44 i52 For benzenesulphonyl azide the values were 0-96, 1-00 and 0-69 respectively . In a similar experiment, ring substitution in p-xylene by / -toluenesulphonylnitrene was shown to take place 2-2 times as rapidly as in benzene When //-toluenesulphonyl azide was decomposed in an equimolar mixture of benzene and cyclohexane at 165°, it was found that the benzene double bond is about eight times more reactive than a G—H bond in cyclohexane . ... 

Phenyl azide and di-iron nonacarbonyl react rapidly in benzene at room temperature (as compared with thermolysis of PhNg alone which occurs at temperatures of 140-170° ). The principal product was the orange phenyl nitrene-complex (387) which decomposed spontaneously in solution to give the urea-based complex (388). Also obtained in low yield was the orange complex (389). The yield of azobenzene was reported to be negligible. C)n the other hand, when the decomposition was carried out in benzene under reflux in the presence of Fe3(CO)i2j a significant amount of azobenzene was found . ... 

Decomposition of 9-(l-azidoethylidene)fluorene (49) in refluxing benzene led to high yields of the spiroazirine 50 2. in contrast, pyrolysis of tlae terminal vinyl azide, 9-(azidomethylene)fluorene (51) in benzene led to only one identifiable product, 9-(A, A -fluorenylidene-aminomethylene)fluorene (52), which was isolated in 25% yield 2. 

Gas-phase pyrolysis of 1,2,3-triazoIe produced vinyl azide and its decomposition products (83JA7681). 4-Diazo-l,2,3-triazole (20) (prepared by dia-zotizing 4-aminotriazole in water), when refluxed in benzene, gave 4-phenyl-1,2,3-triazole (53% yield) and a mixture of cyanobicycloheptatrienes (15%). Photolysis proceeded similarly, except that the latter products preponderated (82TL5115). 

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