Iodine azide Subject

One of the best known reactions of 1-azirines is the acid/catalyzed hydrolysis to aminoketones. Since the Neber reaction also accomplishes this same synthetic end, this reaction may appear to have little practical value. This is not the situation because with the Neber reaction there is no control over the aminoketone that will be obtained from a given ketone. For example, when oxime (127) derived from benzyl methyl ketone (126) is subjected to the Neber reaction aminoketone 128 is obtained.59 The amino function is substituted for the most acidic a-hydrogen. The isomeric aminoketone (132) that could not be prepared by the Neber reaction can be formed by the hydrolysis of 1-azirine (131). The synthesis of this 1-azirine has been accomplished from allyl benzene (129) through vinyl azide (130) using iodine azide.22... 

A better method for the preparation of the terminal isomers has resulted from the observations that bromine azide, unlike iodine azide, may be induced to add to olefins by a free-radical mechanism . Thus, when styrene was subjected to the addition of bromine azide in pentane a quantitative yield of the precursor 23 for the terminal azide was obtained, while reaction in a more polar solvent gave a very high yield of the opposite regioisomer 24. 

In reactions with azides, ketones are directly converted to 5-hydroxytriazolines. Ketone enolate 247, generated by treatment of norbornanone 246 with LDA at 0°C, adds readily to azides to provide hydroxytriazolines 248 in 67-93% yield. Interestingly, l-azido-3-iodopropane subjected to the reaction with enolate 247 gives tetracyclic triazoline derivative 251 in 94% yield. The reaction starts from an electrophilic attack of the azide on the ketone a-carbon atom. The following nucleophilic attack on the carbonyl group in intermediate 249 results in triazoline 250. The process is completed by nucleophilic substitution of the iodine atom to form the tetrahydrooxazine ring of product 251 (Scheme 35) <2004JOC1720>. 

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