Azides diene double bonds

The addition of iodine azide to double bonds gives p-iodo azides. The reagent can be prepared in situ from KI—NaNa in the presence of Oxone -wet alumina. The addition is stereospecific and anti, suggesting that the mechanism involves a cyclic iodonium ion intermediate. The reaction has been performed on many double-bond compounds, including allenes and a,p-unsaturated ketones. Similar reactions can be performed with BrNa and CfNa. 1,4-Addition has been found with acyclic conjugated dienes. In the case of BrNa, both electrophilic and free-radical mechanisms are important, whUe with CIN3 the addi-... 

Iodine azide is a highly selective reagent addition to the 16-double bond of androsta-4,16-diene-3-ones is possible and some selectivity in addition to the 16-double bond of A -dienes has been observed.Hydroxy groups in the steroid should be protected, e.g., by acetylation, since in some instances oxidized side products are formed. 

Vogel and Delavier (26) reported a synthesis of the 6-azabicyclo[3.2.2]nonane skeleton 130 using an intramolecular azide-alkene cycloaddition strategy (Scheme 9.26). When refluxed in xylene, the azide 126 underwent an intramolecular 1,3-dipolar cycloaddition with the internal alkene. Nitrogen extrusion and subsequent rearrangement led to a mixmre of compounds 128, 129, and 130. Reactions of azides with the double bond of dienes were also used in various total syntheses of alkaloids, and will be discussed later in Section 9.2.2. 

The Dewar thiophene (2), possessing a strained double bond substituted with highly electronegative groups, undergoes cycloaddition with dienes (77JCS(P1)2355) and azides... 

Regioisomerism in azide additions is also evident in unsymmetrical dienes with two unequally strained double bonds.89,92,144 Reaction occurs preferentially at the angle-strained double bond,25,81,89-92 and two isomeric exo-monotriazoline adducts are obtained.81,93 The ratios of the triazoline isomers from the reaction of phenyl azide and bicycloocta-2,6-diene, as deduced from their NMR spectra, indicate that the major isomer is the one that results from the terminal azido nitrogen attacking the olefinic carbon more removed from the unreactive double bond (Scheme 10).92 Similar reactions... 

The addition of aryl azides to cyclic dienes in which both double bonds are strained, leads to the formation of mono- or bistriazoline adducts.25,97,98,104,115,146-148 A monoadduct is not obtained from the reaction of trimethylsilyl azide and norbornadiene, inasmuch as it is less stable than the bisadduct and undergoes a retro Diels-Alder reaction (Section IV,A,5).104 The formation of two exo isomers of the bisadduct, with the trimethylsilyl groups in the syn and anti positions, is indicated by the NMR spectrum,104 although the isolated product is the anti isomer. 

An important synthetic route to aziridines is the decomposition of organic azides to the correspondic nitrenes by loss of nitrogen. However, depending on the nature of both, the azide and the alkene and on the experimental conditions, the 1,3-cycloaddition of the azide group to the alkene double bond may occur to give a dihydro triazole, which can be converted in situ or after isolation to the aziridine. Furthermore, /3-functionalized amines are obtained from certain dihydro triazoles, or directly by reaction of azides with certain alkenes, and dihydropyrroles are obtained by reaction of azides with dienes, hence these topics will be treated separately (Section 7.2.9). 

The first step is the photolysis of the azide giving a nitrene which forms a dihydrobenzazirine 13 by a [1+2] cycloaddition with the arene the latter isomerizes yielding 1//-azepine. An alternative synthesis of l//-azepines 14 is based on bicyclic aziridines 15, which are transformed to 14 by addition of bromine to the double bond, two-fold dehydrobromination and valence tautomerization of the resulting 13. The bicyclic aziridines 15 are available from cyclohexa-1,4-dienes via l-alkoxycarbonylamino-2-iodocyclohexenes 16 and their SNi-cyclization [15]. 

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