Aroyl azides

TABLE 11-22- l-AROYL-2-(2-THIAZOLYL) HYDRAZINES FROM AROYLTHIOSEMICARB AZIDES"... 

Several approaches to the 1,2,3-triazole core have been published in 2000. Iodobenzene diacetate-mediated oxidation of hydrazones 152 led to fused 1,2,3-triazoloheterocycles 153 <00SC417>. Treatment of oxazolone 154 with iso-pentyl nitrite in the presence of acetic acid gave 1,2,3-triazole 155, a precursor to 3-(W-l,2,3-triazolyl)-substituted a,P-unsaturated a amino acid derivatives <00SC2863>. Aroyl-substituted ketene aminals 156 reacted with aryl azides to provide polysubstituted 1,23-triazoles 157 <00HC387>. 2-Aryl-2T/,4/f-imidazo[43-d][l,2,3]triazoles 159 were prepared from the reaction of triethyl AM-ethyl-2-methyl-4-nitro-l//-imidazol-5-yl phosphoramidate (158) with aryl isocyanates <00TL9889>. 

The aroyl-substituted heterocyclic ketene aminals 482 react with 4-chlorophenyl azide to give polysubstituted 1,2,3-triazoles 483 and imidazo[ 1. Z-r 1.2,4]triazoles 39 (Equation 112) <2000HAC387>. Polysubstituted 1,2,4-triazoles are formed by the nucleophilic attack of the ct-carbon of the azide. Then, through the cyclocondensation and aromatization sequences, the fused heterocycles resulted by a 1,3-dipolar addition at first, and then through a Dimroth rearrangement and deamination of chloroaniline <1992JOC184>. 

A sulphamoyl azide has also been used in the synthesis of a phosphazenyl-stabilized ylide (16).28 Aroyl azides react readily with triarylphosphines to give phosphazenes... 

The reaction of sodium azide with N-aryl chloroimines, obtained from benzanilides and thionyl chloride, to form 1,5-disubstituted tetrazoles is catalysed by tetra-n-butyl-ammonium bromide (Scheme 5.26, Table 5.40) [18] in variable yields, but generally <85%. 5-Butyl-2,3-diphenyltetrazolium salts have also been used as catalysts [18, 19]. 1,5-Disubstituted tetrazoles are also obtained from a one-pot sequential reaction of carbodimides with sodium azide and an aroyl chloride in the presence of tetra-n-butylammonium chloride [20]. 5-Chlorotetrazoles are obtained from the catalysed reaction of aryldichloroisocyanides with sodium azide (Scheme 5.26) [21],... 

The addition of nitrenes leads predominantly to the closed [6,6] bridged isomers. The corresponding [5,6] bridged isomer is - if at all - formed only in small amounts, probably via a direct addition to the [5,6] bond [394]. Nitrenes have been generated by thermolysis of azido-formic esters [172,395 00], photolysis of aroyl azides [401] or aryl azide [402], elimination of O-4-nitrophenylsulfonylalkylhydroxamic acid [403] or reaction of amines with Pb(OAc)4 [404]. 

Zinc chloride-doped natural phosphate was shown to have catalytic behavior in the 1,3-dipolar cycloadditions of nucleoside acetylenes with azides to form triazolonucleosides <99SC1057>. A soluble polymer-supported 1,3-dipolar cycloaddition of carbohydrate-derived 1,2,3-triazoles has been reported <99H(51)1807>. 2-Styrylchromones and sodium azide were employed in the synthesis of 4(5)-aryl-5(4)-(2-chromonyl)-1,2,3-triazoles <99H(51)481>. Lead(IV) acetate oxidation of mixed bis-aroyl hydrazones of biacetyl led to l-(a-aroyloxyarylideneamino)-3,5-dimethyl-l,2,3-triazoles <99H(51)599>. Reaction of 1-amino-3-methylbenzimidazolium chloride with lead(fV) acetate afforded l-methyl-l/f-benzotriazole <99BML961>. Hydrogenation reactions of some [l,2,3]triazolo[l,5-a]pyridines, [l,2,3]triazolo[l,5-a]quinolines, and [l,2,3]triazolo[l,5-a]isoquinolines were studied <99T12881>. 

In subsequent work, Sigman et studied aroyl azides 14 and 17-18. 

Each of these azides contains an internal sensitizing group. Upon LFP the triplet states of all three azides are observed. However, in the case of 17 and 18, only singlet nitrene derived products are formed. Photolysis of 17 and 18 at 8 K in fluorolube fails to produce persistent triplet EPR spectra. It seems clear that these aroyl nitrenes also have singlet ground states. As mentioned previously, photolysis of 14 does produce a triplet nitrene EPR spectrum. 

Protonation of aroyl azides and a-ketonitriles in superacid media (HS03F-SbF5, 78°C) occurs exclusively on the oxygen to yield a-azidocarboxonium ions 374688 and a-cyanocarboxonium ions 375,689 respectively. 

The related reagent combination, PhI(OAc)2/NaN3, has been employed for direct conversions of aromatic aldehydes to aroyl azides, ArCON3 [31]. These reactions were conducted in dichloromethane at room temperature and are thought to occur by a radical mechanism. 

Acyl azides which produce the nitrenes 3 and 4 upon photolysis are the most suitable for synthetic applications of cycloaddition reactions. Therefore, this subchapter will mainly deal with alkoxycarbonyl and aroyl nitrenes. 

Aroyl nitrenes can be generated from their corresponding azides by three methods ... 

The combination of nitrene and substrate chirality improves the diastereoselectivity of the cycloaddition reaction. For example, due to the use of both chiral aroyl azides and chiral alkenes, the pure exo-product (compound 108) was obtained (Sch. 32) [43]. 

Kym, P. R. Anstead, G. M. Pinney, K. G. Wilson, S. R. Katzenellenbogen, J. A. Molecular structures, conformational analysis, and preferential modes of binding of 3-aroyl-2-arylbenzo[b]thiophene estrogen receptor ligands LYl 17018 and aryl azide photoaffinity labeling analogs, J. Med. Chem. 1993, 36, 3910-3922. 

This method has been exploited for the functionalization of [60]fullerene by using several aroyl azides166 and [2.4,6-tri-(tm-butyl)phenyl]oxycarbonyl azide16, which afforded the corresponding A -acylaziridines and subsequently the dihydrooxazoles, whereas azafulleroids were produced with [2-(trimethylsilyl)ethoxy]methyl azide and several benzylic azides presumably through the thermal decomposition of the intermediate dihydrotriazoles77. 

Aroyl azides (ArCON3) have been studied by some Japanese workers Benzoyl azide is reported to have a maximum at 245-5 nm while substitution in the para position causes a shift to longer wavelength. Methoxy changes the maximum to 283 nm while fluorine moves it to 251 and nitro to 260-5. Other substituents such as Cl, Br, I, methyl, and CON3 caused the maximum to fall between that of the p-Y and -OMe derivatives. 

A. Alkanoyl, Alkenoyl and Aroyl Azides I. Preparation and properties... 

Azides of the type RCON3 are colourless liquids or solids. Alkanoyl and alkenoyl azides are often prepared, but rarely isolated because they undergo Curtius rearrangement already at or below room temperature. Aroyl azides are much more stable thermally. 

Acyl azides can be decomposed by reaction with free radicals. In methanol, ethoxycarbonyl azide requires one equivalent of radical initiator (diethyl peroxydicarbonate) to decompose one mole of the azide but in alcohols that are better hydrogen donors, chain reactions occur Homer2 studied the dehydrogenation of isopropanol by aroyl, carbamoyl and alkoxycarbonyl azides ... 

Insertion into N—bonds by alkoxycarbonylnitrenes is a facile reaction, but is hampered by nucleophilic displacement of azide ion when alkoxycarbonyl azides are used as the nitrene precursor. Haf-ner obtained a 52% yield of phenylhydrazoformate, PhNHNH-COOC2H5, by thermolysis of ethyl azidoformate in aniline Aroyl azides have also been used Horner obtained a 14% yield of N-phenyl-iV -benzoylhydrazine by photolys ng benzoyl azide in aniline. With more nucleophilic amines, it is better to use the a-elimination route to alkoxycarbonylnitrenes . Using this method, yields of... 

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