Azides alkoxycarbonyl—

With acyl and alkoxycarbonyl azides, 2 -triazoles are isolated, although the l.ff-isomers are detected as intermediates. The reaction is not very general it fails with the corresponding sulfonium ylids, and fairly minor changes in substituents on the phosphorus ylid result in the formation of diazoketones rather than triazoles. ... 

JV-Alkoxycarbonyl- and iV-arenesulfonyl-imines can be prepared by the reaction between pyridines and nitrenes, the latter being generated from the corresponding azides (72JOC2022, 64TL1733). Thermolysis of pyridinium iV-acylimines gives isocyanates and the parent heterocycle <79JCS(P1)446). 

A wide range of organic azides such as alkyl,80 alkenyl,79,100 aryl, including dinitrophenyl and picryl,101-103 heterocyclic,28,91 trimethylsilyl,79,104 acyl,9 phosphoryl,105 sulfonyl,106 alkoxycarbonyl,9 and oxime azides107 has been found to add to norbornene,25,79,90,104,105,107-121 its derivatives,104 106,1 13,120,122-128 or to related bridged bicyclic... 

With acyl and alkoxycarbonyl azides, 2//-triazoles are formed by isomerization of the 1H compounds,410 and changes in R1 and R2 substitution lead to diazo compounds and iminophosphoranes rather than triazoles,408,411,412,415 owing to competitive addition to the C=P bond. Reaction of cyanogen azide with a-acylphosphorus ylides leads to 1-cyanotriazoles, which undergo in situ ring opening to give N-cyano-a-diazoimines.417... 

Acyl nitrenes are highly reactive but unfortunately their precursors, acyl azides, are chemically reactive, e.g. they acylate amino groups. While sulfonyl- and alkoxycarbonyl azides are somewhat less reactive than acyla-zides, and the nitrenes derived from them are highly reactive (Lwowski, 1970 and for sulfonyl nitrenes see Abramovitch et al., 1981 and references therein), the azides must be irradiated in the UV, below 300 nm. Phos-phorylnitrenes are the most reactive nitrenes known and will insert into CH bonds in the presence of hydroxyl groups (Breslow et al., 1974). Again, photolysis occurs at ultraviolet wavelengths. 

Scheme 1.19 Sidewall functionalization of SWCNTs by [2+1]-cycloaddition of alkoxycarbonyl nitrenes obtained from azides.

Sidewall functionalization of SWCNTs was achieved via the addition of reactive alkyloxycarbonyl nitrenes obtained from alkoxycarbonyl azides. The driving force for this reaction is the thermally-induced N2 extrusion. The nitrenes generated attack nanotube sidewalls in a [2+l]-cycloaddition forming an aziridine ring at the tubes sidewalls (Scheme 1.19). 

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. 

Rearrangement of alkoxycarbonyl imidazole acryl azides in diphenyl ether at high temperatures afforded imidazo[l,5-c]pyrimidinone or imidazo[4,5-c]pyridinone derivatives <02TL5879>. Efficient synthesis of imidazopyridodiazepines from peri annulation in imidazo[l,2-a]pyridine has been described <02TL9119>. A convenient synthesis of 3,6-disubstituted-2-aminoimidazo[l, 2-a]pyridines has been published <02TL9051>. Novel 2,3-dihydroimidazo[2,l-h][l,3]oxazoles were prepared from intramolecular nucleophilic i/wo-substitution of 2-alkylsulfonylimidazoles <02S2691>. 4,4 -Bi-l//-imidazol-2-ones were efficiently synthesized from 5-amino-ot-imino-1 //-imidazole-4-acetonitriles and isocyanates <02JOC5546>. 

Alkoxycarbonyl azides, which do not readily undergo the Curtius rearrangement, have a much richer triazoline and nitrene chemistry, the scope and theory of which are frilly discussed by Lwowski. Carb-ethoxynitrene may be generated by a-eliminations, c tiorudly assisted by ultrasound or PTC (Scheme 23). - ... 

By cycloaddition of alkoxycarbonyl azides to the silyl enol ether of ( )-5-extj,6-exo-[isopropy-lidenebis(oxy)]-7-oxabicyclo[2.2.1]heptan-2-one 28, /V-protected 3-exoamino ketones 29 were prepared56. The exo relative configuration of the nitrogen-substituted carbon center was established by H NMR. 

The addition of alkoxycarbonyl nitrenes, generated photochemically from azides, to substituted dihydropyrans and tri-O-acetyl-D-glycal57"59 in alcoholic solution gave the products of alcoholysis 30 and 31-33 of the intermediate aziridines by a one-pot procedure59. The attack of the nitrene takes place mainly on the less hindered face of the double bond, but complete control of the diastereoselectivity was not accomplished even the ring opening of the aziridine can follow both anti and syn stereochemistry. 

The intramolecular aziridination of alkoxycarbonyl azides derived from ( )-5-hydroxymethyl-2(5//)-furanone, via thermal decomposition to nitrenes, gave the tricyclic compound 34 which was successively converted to the bicyclic compound 35. The aziridine ring opening with hydrazoic acid/ sodium azide ion of the aziridines 34 and 35 gives azido lactones 36 with the xylo configuration mixtures of xylo- and (y.w-forms were obtained by partial epimerization in equilibrating conditions and were easily separated60. 

Reaction of aryl azides with hydrazine hydrate can result in reductive cleavage of the azido group. Azidobenzene gives a mixture of benzene and aniline when heated with an excess of hydrazine hydrate in ethanol. If there is an acyl or an alkoxycarbonyl group at the ortho position, cyclization products are formed instead for example, methyl 2-azidobenzoate gave indazolinone (13 90%). 

Carboxy includes carboxy (carboxylic acids), alkoxycarbonyl (esters), carbamoyl (amides), thiocarbamoyl, hydrazinocarbamoyl (hydrazides), guanidinocarbonyl, azidocarbonyl (azides), chlorocarbonyl (acid chlorides), amidino, C-hydrazino-C-iminomethyl, C-alkoxy-C-iminomethyl (imino ethers), C-alkylthio-C-iminomethyl (iminothioethers), cyano (nitriles), C-formyl(aldehydes), dialkoxymethyl (acetals of aldehydes), C-acyl (ketones), isocyanato, and thiocyanato groups. 

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... 

The addition of carbenes and carbenoids to imines and nitriles continues to be a popular approach to aziridines and 2//-azirines. These processes have been well reviewed by Deyrup (B-83MI101-01). Dichlorocarbene and other dihalocarbenes have been added to a wide variety of imines to provide dihaloaziridines. A recent example is shown in Equation (64), illustrating the use of phase-transfer conditions <93H(36)69i). The treatment of azides with excess dichlorocarbene results in the formation of the 2,2,3,3-tetrachloroaziridines (92TL2339). Presumably, the azide is converted by dichlorocarbene to the imidoyl dihalide RN=CC12 which reacts further with dichlorocarbene. Transition metal-promoted reaction of a-diazoesters with imines provides 2-(alkoxycarbonyl)aziridines [Pg.46]

Nitrenes generated photochemically or thermally from arenesulfonyl azides and alkoxycarbonyl azides add to the nitrogen atom of heteroaromatic bases to give the corresponding N-(substituted imines).20,21,50,64-69 However, the yields are usually low and the scope is severely limited. 

Nitrenes addition Sidewalls Molecules with alkoxycarbonyl azide groups — —... 

Although the formation of aziridines from olefins and azides may not in all cases involve a nitrene intermediate, some recent literature reports of reactions of this type have for convenience been included in this section (see also the section on ring contraction). Alkoxycarbonyl nitrenes (R = Me or Et),... 

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