Thermolysis azides

The concentration of alkyl azidoformate used in these decompositions is important since with an excess (0.5 molar equiv) of azide, thermolysis at 130°C results in the formation of 1 2 1 //-azepine (methoxycarbonyl)nitrene adducts as the major products.145,146... 

This indicates that the prebaking temperature higher than the melting point of the azide decomposes the azide (50%) and it totally decomposes upto 100 mJ/cm2 irradiation. It is possible that subsequent reactions of the nitrene, generated from the azide thermolysis and photolysis, with the styrene resin could be responsible for solubility modulation of this type resist (16). 

The intramolecular 1,3-dipolar cycloaddition reaction of azides has become an increasingly useful process for the construction of natural products and molecules of theoretical interest.192 193 For example, 2-substituted azido enone (238) was prepared from the corresponding bromide by treatment with sodium azide. Thermolysis of this material afforded aziridinyl ketone (240) presumably via a transient dipolar cycloadduct (239).193 Ketone (240) was subsequently converted to an intermediate previously used to prepare histrionicotoxin (241 Scheme 56). 

Aryl Azide Thermolysis "A Series of Rather Involved Rearrangement Reactions"... 

One of the first examples of azide thermolysis cyclization reactions was demonstrated in the synthesis of biologically active benzofuroxanes.49 The cyclization of aryl azides 51 based on the ortho-nitro resins 50 was achieved at ca. 70° to give the benzofuroxanes 52 (Scheme 9). 

Nitriles add carbonylnitrenes to form 1,3,4-oxadiazoles . Alkoxycarbonylnitrenes (made either by azide photolysis, azide thermolysis or by the a-elimination route) give the 2-alkoxy-1,3,4-... 

Thermolysis of orffto-azido-styrenes gives nitrenes that insert into the side-chain to form indoles. Similar nitrenes have been generated by reaction of nitro-compounds with trialkyl phosphites. The azide thermolysis method can be used to prepare 2-nitroindoles. ... 

Indazoles may be assembled via thermolysis as well. Treatment of diphenylcarbamoyl chloride with sodium azide gives rise to diphenyl-carbamoyl azide. Thermolysis of the diphenyl-carbamoyl azide then afforded indazolol. Subsequent alkylation of the indazolol then produced a series of indazole derivatives as activators of the nitric oxide receptor, soluble guanylate cyclise. 

Evidence for nitrene intermediacy comes from kinetic analyses that show reactions of this type to be strictly first order in aryl azide. Thermolysis of aryl azides in more reactive solvents, which contain an olefmic double bond, does not involve the intermediacy of a nitrene. A kinetic study of the thermolysis of p-anisyl azide in indene indicated a concerted loss of nitrogen and no evidence could be found for the formation of a triazoline. This is surprising as azides are well known to add to olefins to give triazolines in other systems. Loss of nitrogen without nitrene involvement is also observed in the decomposition of aryl azides bearing certain o-substituents (e.g., nitro, phenylazo, and carbonyl or thiocarbonyP ) for instance, thermolysis of o-nitrophenyl azide gives benzofuroxan ... 

One instance of 2,4-disubstitution of an aromatic nucleus, by pen-tafluorophenylnitrene, has been recorded, the product so formed subsequently undergoing oxidative cyclization. Intermolecular aromatic substitution so far has been reported only on deoxygenation of nitro and nitroso aromatics and azide thermolysis ... 

Hafner and Bauer were able to isolate azirine 254 in high yield from a low-temperature photolysis of the corresponding vinyl azide. Thermolysis of 254 gave imine 285 and fluorenone 286. The thermal reaction was proposed to proceed via the 9-fluorenylidene carbene, produced by elimination of HCN from 254 followed by a subsequent reaction with starting material or with oxygen. 

In view of the presence of unsaturated -electrons in CNTs, Smalley and coworkers and Holzinger et al. have functionalized the sidewall of SWCNTs directly by fluorination and azide-thermolysis, respectively. Direct addition of functionalities to the CNTs was enabled by nitrene cycloaddition, nucleophilic carbine addition, and radical addition. 

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