Bromine azide aziridine synthesis

The alkene pseudohalogen adducts (15) of Scheme 8 are also useful intermediates for aziridine synthesis. These adducts are discussed later in Sections 3.S.6.2-4. The iodine azide and bromine azide adducts may be reduced to aziridines with many reagents recent references report use of lidiium aluminum hydride - and dimethylamineborane. The iodine isocyanate aziridination continues to prove useful, as in Scheme Since the recent reviews, - the mechanism of the triphenylphosphine-based... 

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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