Benzoyl azide, rearrangement

The thermal Curtius rearrangement of formyl, acetyl, and benzoyl azides was studied by DFT.78 The authors conclude that the reaction occurs by a concerted mechanism and not by the alternative nitrene intermediate. 

Lewis acids may also act as catalysts with an efficiency roughly parallel to that found in Friedel-Crafts and related reactions These rearrangements are first-order in acid and a substrate-acid adduct is believed to be rapidly formed which rearranges in a slow step with concomitant release of catalyst. Adducts of benzoyl azide with boron trichloride and trifluoride have been isolated at low temperatures... 

A striking, but isolated, obsei vation was reported by Horner . He found that direct photolysis of benzoyl azide in ethanol or isopropanol led to the Curtius rearrangement (44%), to insertion (31%) and to some hydrogen abstraction (23%). However, in the presence of small concentrations of benzophenone the photoreaction produced exclusively benzamide, with a quantum yield far in excess of unity. The high yield indicated a chain reaction, benzophenone playing more the part of a photocatalyst than that of a convcndonal sensitizer. 

The reductive cleavage of benzoyl azide rans at low temperature with tetracarbonylhydridofeirate, [HFe(CO)4] and with diphosphorus tetraiodide in benzene under reflux. Curtius rearrangement side products are not observed. 

Reynolds, Van Allen and Borden 31> made use of the photochemical rearrangement of benzoyl azides to phenyl isocyanates to conduct a photopolycondensation. By incorporation of a group, reactive with isocyanates, such as amino, into the same molecule, photolysis led to formation of a polyurea structure. 

The thermal Curtius rearrangement of benzoyl azide in the presence of Lewis acids was studied using DFT. ... 

Other types of bonds undergo sonolysis, for instance the nitrogen-nitrogen bond of an azido group. The Curtius rearrangement of benzoyl azide is probably one of the first attempts to use sonication in an organic reaction. 3 phenyl isocyanate is... 

Heating benzoyl azide with ethanol or benzoylhydrazine gave the corresponding urethane (5) or benzoylphenyl semicarbazide (6), respectively. The explosive diacyl azide 8, prepared from fumaric acid-derived 7, underwent double rearrangement in ethanol to the dicarbamate 9. ... 

Figure 2 Rate constants and activation parameters for Curtius rearrangement of benzoyl azides...

The structures of donor-acceptor complexes of iyn-benzoyl azide, its 2-methyl- and 2,6-dimethyl-substituted derivatives with BF3, AICI3, and SbCls, and the transition states of the rearrangement into isocyanates have been reported by computational methods. The reaction of donor-substituted alkenes with a-diazo-a-nitro ethyl acetate under Rh catalysis have been reported which show that the nitro group is inserted forming cyclic nitronates, whereas the ester moiety was not incorporated into the ring system (Scheme 198). ... 

The yields of the isocyanates produced upon photolysis of benzoyl azide (R=Ph, 31b) and its pam-methoxy, para-chloro and meta- uoro derivatives were found to be in the range of 40-50% in both inert solvents and in solvents that intercept acylnitrenes. Similar results were obtained for 2-naphthoyl azide (35). Irradiation of 35 in cyclohexane at room temperature produces isocyanate (36, -45%), A-cyclohexyl-2-naphthamide - the product of 2-naphthoylnitrene (37) insertion (-50%), and a trace (<1%) of 2-naphthamide (38). Therefore, it was concluded that carbonylnitrenes (R-CO-N) do not rearrange to isocyanates (R-N=C=0) at a rate that is competitive with their capture by trapping agents. ... 

In hot ethanol, benzoyl azide was converted to ethyl A-phenylcarbamate (1894). This Curtius rearrangement was recognized by its discoverer as a general method of degrading carboxylic acids to amines, whereas the intermediacy of isocyanates escaped him. 

Other non-traditional preparations of 1,2,3-triazoles have been reported. The rearrangement in dioxane/water of (Z)-arylhydrazones of 5-amino-3-benzoyl-l,2,4-oxadiazole into (2-aryl-5-phenyl-27/-l,2,3-triazol-4-yl)ureas was investigated mechanistically in terms of substituents on different pathways <06JOC5616>. A general and efficient method for the preparation of 2,4-diary 1-1,2,3-triazoles 140 from a-hydroxyacetophenones 139 and arylhydrazines is reported <06SC2461>. 5-Alkylamino-] //-], 2,3-triazoles were obtained by base-mediated cleavage of cycloadducts of azides to cyclic ketene acetals <06S1943>. Oxidation of N-... 

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