Pyrolysis, of azides

Kinetic studies of pyrolysis of azides, giving oxadiazole A-oxides in near-quantitative yields, showed that the 5-azido-6-nitroquinoline pyrolyzed in acetic acid 27.6 times faster than did 5-azidoquinolines, because of the -M effect of the group adjacent to the azide group (85AJC1045). 

The well known pyrolysis of azides and the reaction of IV-chlor-amines with soda lime are regarded as rearrangements of a nitrogen diradical ... 

H. Bock and R. Dammel, Angew. Chem., 99, 518 (1987) Angew. Chem., Int. Ed. Engl., 26, 487 (1987), demonstrate the usefulness of PE spectroscopy in studies of gas-phase pyrolysis of azides and report on information obtained concerning the pathways of thermal fragmentation. 

Another four-membered phosphazene ring (126) has been prepared by pyrolysis of azide (125) (Cp = CsMes, Mes = C6H2Bu 3-2,4,6). Metallation of (126), followed by protonation with Bu OH gives the tautomeric cyclodiphosphazane (127). ... 

Bock, H. and Damme1, R. (1987) The Pyrolysis of Azides in the Gas Phase Angewante Chemie International Edition (English) 26, 504-526. 

Perhaps one of the most exciting developments in the chemistry of quinoxalines and phenazines in recent years originates from the American University of Beirut in Lebanon, where Haddadin and Issidorides first made the observation that benzofuroxans undergo reaction with a variety of alkenic substrates to produce quinoxaline di-AT-oxides in a one-pot reaction which has subsequently become known as the Beirut reaction . Many new reactions tend to fall by the wayside by virtue of the fact that they are experimentally complex or require starting materials which are inaccessible however, in this instance the experimental conditions are straightforward and the starting benzofuroxans are conveniently prepared by hypochlorite oxidation of the corresponding o-nitroanilines or by pyrolysis of o-nitrophenyl azides. 

Perfluorotetramethylthiadiphosphanorbornadiene and bis(trifluoromethyl) thiadiphosphole can be prepared by thermolysis of an adduct of methanol and hexakis(trifluoromethyl)-l,4-diphosphabarrelene with sulfur [113] (equation 23) Pyrolysis of the adduct of hexafluorinated Dewar benzene and phenyl azide results in ring expansion giving azepine, which photochemically yields an intramolecular 2-1-2 adduct, a good dienophile for the Diels-Alder reaction [114, //5] (equation 24) Thermolysis of fluonnated derivatives of 1,5-diazabicyclo-... 

Ring fusion seems to occur in the quinoxaline derivative (28), which has been stated to exist in red and blue-black forms. Other derivatives of type 28 are reported. Attempts to prepare 5,6-furo-xanobenzofuroxan by pyrolysis of the azide (29) met with no success. An early example in the literature of such a linear fused structure was shortly afterward revised to the angularly fused type (17). 

Early attempts to prepare 5-amino- and 5-acylaminobenzofuroxans by hypochlorite oxidation of the corresponding o-nitroanilines met with failure. Pyrolysis of the appropriate azide, however, gives 5-dimetliylamino- and 5-acetamidobenzofuroxan, whereas urethans of type (33) are produced by Curtius degradation of the 5-carboxylic acid. Controlled hydrolysis of the acetamido compound and the... 

Interest in the mechanism and product distribution of thermal and photochemical transformations of aryl azides led to the isolation of some nitrogen-containing derivatives of heptafulvalene. Based on elemental analysis and spectroscopic data it has been suggested tentatively that the compound isolated following vapor-phase pyrolysis of azidopentafluoro-... 

Also unexpected is the formation of the 2,2 -(3,4,5,6,7-pentafluoroazepin-2-ylidene) (35) during the flow pyrolysis of perfluorophenyl azide over platinum at 300 C.6°... 

Pyrolysis of diethyl aluminum azide [(C2H5)2A1N3] at 450-870°C). 

The pyrolysis of aluminum-nitrogen organic complexes, such as diethyl aluminum azide [(C2H5)2A1N3], is also used successfully at low deposition temperatures (450-870°C).0 l Another metallo-organic, hexakis(dimethylamido)dialuminum, reacting with ammonia allows deposition at 200-250°C at atmospheric pressure. 1... 

The Curtius rearrangement involves the pyrolysis of acyl azides to yield isocy-anates. " The reaction gives good yields of isocyanates, since no water is present to... 

Two other results will now be pointed out which presumably also require reinterpretation in the light of the reaction behavior of iminooxophosphoranes. Thus the gas phase pyrolysis of diphenylphosphoryl azide is reported to give monomeric 92 50) and the dehydrohalogenation of phenylphosphoric adamantylamidic chloride with methylhydrazine the heterocumulene 93 51), which is even considered resistant to water. Since partly correct analytical values are available, 92 and 93 may well be oligomers. 

The vapour-phase pyrolysis of benzenesulphonyl azide at 625 °C gave a 17.5% yield of azobenzene 71>, and a trace of the latter was also reported when the azide was heated in boiling cyclohexanone >. 

Internal nitrenes normally react at the adjacent position. Reduction of 2-(2-nitrophenyl)furan by ethyl phosphite yields furoindole derivatives in fair yield (34%) only, whereas much better results attend the pyrolysis of 2-(2-azidophenyl)furan.280 Furopyrazoles are obtained similarly.281 Azidofurans yield nitrenes that insert into adjacent CH links to form furo-pyrroles.282 Quite different results attend either the pyrolysis or the photolysis of azide 107a for the expected insertion into the side chain occurs giving the related indole but it is accompanied by the surprising replacement of furan oxygen by nitrogen producing 107b and similar products.283... 

Banks and co-workers found that gas-phase pyrolysis of pentafluorophenyl azide yields a diazaheptafulvalene (Scheme 16).50 The formation of the product was viewed as dimerization of the perfluoro analogue of 4b, although it is possible that it could, instead, have been formed by dimerization of the corresponding cyclic ketenimine. 

Nitration of various phenyl-49 and benzyl-phosphine60 oxides (59) has been described, and the P=0 group found to be mem-directing49 in the former case. Pyrolysis of the acyl azide (60)51 takes the course shown. 

Photolysis of alkyl azides bearing pendant aryl groups does not lead to intramolecular trapping of a nitrene by the aryl group. However, intramolecular capture of the putative nitrene is observed upon pyrolysis of the azide precursor. These observations convinced Kyba and Abramovitch" ° that 1,2-migration is concerted with loss of nitrogen from the excited state of the azide, but that a free singlet nitrene is formed upon thermal decomposition. The chemistry of acyl azides will be shown later to exhibit the opposite pattern. 

Photolysis or pyrolysis of most aryl azides in hydrocarbons leads to polymeric tars instead of diagnostic insertion products and aziridines. ... 

Phenylazide was first synthesized by Greiss in 1864. In 1912, Wolf studied the pyrolysis of phenyl azide in aniline. The product of this reaction, azepine (27), was identified by Huisgen and co-worker in 1958. Eight years later. Doering and Odum demonstrated that azepine (27) is formed upon photolysis of phenylazide in diethylamine and in 1977 Carroll et al. ° discovered the formation of 28 upon photolysis of phenyl azide in the presence of ethanethiol. 

It was mentioned previously that, unlike most arylnitrenes, polyfluorinated arylnitrenes have bountiful bimolecular chemistry. Banks and Sparkes found that pyrolysis of 4-azido-2,3,5,6-tetrafluoropyridine in cyclohexane produced the product of formal CH insertion in 45% yield. Tetrafluoropyridyinitrene was also captured by alkenes, dimethyl sulfoxide and even benzene. Pyrolysis of perfluorophenyl azide (15e) yields a product of formal insertion with a CH-bond of benzene and the formation of adducts with dimethyl sulfoxide.Abramovitch et demonstrated that... 

Pyrolysis of alkyl or aryl azides 8-18 Reaction between oxime sulfonates and organometallic compounds... 

The vapor phase pyrolysis of vinyl azides leads to the formation of 2-Bub6tituted-l-flairinea 2 Eq. 87). 

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