Azides, alkoxycarbonyl reactions

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). 

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... 

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. 

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%). 

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]

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),... 

Ethoxycarbonylnitrene (generated photochemically from the azide) also reacts with 4-t-butylthian, affording a nearly 1 1 mixture of both cis- and trans-sulphimides. This non-stereoselectivity in the reaction of the nitrene is in marked contrast with that of the reaction of carbenes with the thian the thian reacts with both bis(alkoxycarbonyl)- and bis(diacetyl)-carbenes, giving the trans-yMes as the sole products (see Vol. 4, p. 112). Various sulphimides of cyclic sulphides, e.g. thians, cis- and frans-thiadecalins, oxathians, and dithians, can be prepared by treating the sulphides either with anilines and AT-chlorosuccinimide or with Bu OCl. In this reaction, the formation of (33 R = Bu , = /7-ClCjH4) with an equatorial... 

Enantioselective imidation of alkyl aryl sulfides with A -alkoxycarbonyl azides as a nitrene precursor is effected by using (OC)Ru(salen) complex as catalyst. The steric and electronic nature of the Af-alkoxycarbonyl group strongly affect the enantioselectivity and the reaction rate. In a systematic and well-executed study of ligand effects on Lewis-acid-catalyzed Diels-Alder reaction, it has been shown that the attachment of aromatic a-amino acid ligands to copper(II) ions leads to an increase in the overall rate of the Diels-Alder reaction between 3-phenyl-l-(2-pyridyl)-2-propene-l-one (Din) and cyclopentadiene... 

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